He just would rather be angry.
It's not that he would rather be angry, it's becuse he simply can't sawitch off his frustration. These kids are incredibly self-focussed and although WE know this is not "good manners" it is, for these kids, the two-year-old inside them that has not yet learned self-control. They do get there, but it takes years longer.
A couple of things to add to what you said - you asked him for a good night. You couped that with "I love you" which risks implying to him that you only love hi when he's good. These kids do need an incentive to try to hold it together, but they do need to know (and be told) that they are loved unconditionally. Otherwise at some level, they will test it.
Also, when you have a good night (even if it's not perfect) simply say so. "Thank you, darlnig, for making an effort to not argue tonight. I could see you were struggling, but you did a good job. Even if you weren't perfect at it - you tried, and I really value that."
Also say the same thing to his dad, if it's appropriate.
Another thing to always remember - treat him as you treat your husband or any other adult in the same situation. These kids don't understand the different way we treat our children. And when he's an adult he will need to understand the right way to treat people. So begin now, with the "he is an adult in miniature" attitude to him. It sets the example for how he should treat you, too.
Think - if this were an adult close friend who was being forced to live with you (perhaps otherwise on the streets due to poverty) then how would you negotiate the house rules? How would you talk to your friend, even if your friend was being very annoying (but maybe not realising it)?
We have similar problems with the family computer. difficult child 3 has even gone to the lengths of scavenging the street clean-ups for discarded computers, then fixing up what he finds for his own use. We let him because it is good training for him. And we really can't argue against it because his first ever computer when he was a baby, was one we ourselves scavenged.
Having your son earn computer time is a good carrot. If you can, try to find a game you can play with him (one of our family favourites is a computer-based board game, similar to Mario Party which is another good option) then make time to play this with him as reward for tantrum-free days.
as for "his treats worked and we backed down" - this puts your interactions on the level of competition, and once you feel you are competing with your child, you will lose. So avoid any sense of competition, and if you find yourself resisting because you think "he will feel he has won" then recognise, you have probably already lost, and so has he.
These kids are very, very good at logic, at reasoning and at 'rules' as they interpret them to be. So if by the rules they have observed, they feel you are being unfair, they won't let you forget it. So you need to really work hard to be fair. And let him see that you are working hard at it.
Our own rule concerning the family computer - difficult child 3 can have moderately free access to it during the day for schoolwork. In the evenings we also let him have access, but only if we don't need it ourselves. If we do, we ask him to get himself off our computer as soon as he can/ We don't insist on immediate vacation of it, because if he's in the middle of something he needs time to get to a point wherehe won't lose data or similar.
An example from my own game play - there is a word game I play (actually trying to gain points on difficult child 3's behalf) and if I'm in the middle of a round, I cannot pause it, I have to keep playing. But I can complete a round in a few minutes. At that point I can leave the game idle indefinitely. If someone came to me and said to me, "Quick! Get off tat computer now! I have to send an email!" I would feel very resentful and angry, even if there wasn't a level of rage already simmering.
Over time, the child learns that you are respecting his time and game play but also requiring a certain amount of responsibility in return. The child begins to be less reactive when you say, "I need you to leave that as soon as you can do so reasonably, to eat your dinner/have your bath/go to bed/do your homework."
If you need extra help, do what we did - stick a Post-It note on the computer screen with your request and when you asked. For example, "6.10 pm - dinner will be ready by 6.20 pm."
That way he can't say, "You never told me!"
Because if you try to tell them sometimes when they are concentrating on something else and answer distractedly, "yeah, sure, uh-huh, ok," without taking their eyes off the screen, they really will not remember being told.
If he's home alone for so long, then assume he will be on the computer. Let him know that you are counting that time towards his fair share. You and husband don't get as long at it and also deserve your fair share, but you are all housemates and need to negotiate with one another. To negotiate respectfully is the social lesson he needs to learn. So you need to set the example for him and negotiate with him. I know it's for you to have access to your own computer, but that is part odf the argument you use - "Daddy & I need to do our own stuff on this computer because we need it for work and we need to do banking, purchasing online etc which is necessary to keep the household funcrtioning. While we do like gaming too, we don't get the same opportunity because we also have to meet the responsibilities on behalf of the family. Any help you can give us will increase the computer time for all of us, which of course will be a lovely thing."
We use a token system of rewards, mostly for schoolwork completed. We have a time factor in it as well - if he competes what I consider to be a fair day's worth (previously negotiated as such and defined) then he earns a credit 9as long as he completes it within one day). If he does any work on a non-school day (also carefully defined - a half-day is counted as a non-school day for tis purpose) then he can credit that work to the adjacent school day of his choice. So if he does a lot of work over the school holidays, then he can credit it all to the next school day (first full day of term) and earn a stackload of credits from me. It's as complex as it is, because it is what difficult child 3 & I have worked out together as being fairest.
SO whatever you and difficult child work out between you, let him know that it is still able to be tweaked if he feels it isn't quite right yet. And you also can suggest changes to him. But you must both agree on how to do it, he needs to feel he has some control over the process.
If he truly is Pervasive Developmental Disorder (PDD), he will learn to not use this to manipulate too much, he will actually be honest and fair about it, mostly. He may at times try to slide by and pretend he did his work properly, but in general Pervasive Developmental Disorder (PDD) kids are honest about this sort odf thing, more so than the average kid. It's another good facet of this. And frankly, the more dishonest he is capable of being, the better his long-term prognosis! He'll cope better in society if he is able to tell white lies. Sad, really, but true.
Fingers crossed for you, that your new system won't need too much tweaking.
Marg