I am so so sorry for your hurting mommy heart.
You should be able to get him on your insurance retroactively and it will cover the shots 100%. If not, take him to the county for the shots. Way back when, our insurance did not cover immunizations; so my kids got their shots at the county clinic despite seeing their regular pediatrician for well baby checks. And if I understand correctly - you would be considered more like "foster" parents - so your/husband's income should not factor into benefit decisions - just your daughter's. That said, they may push for baby daddy's info and you may not want to open that door if he isn't on the birth certificate.
But I am getting way ahead of myself. You have a lot on your plate - eat it is small bites, 1 by 1.
difficult child is somewhere safe tonight and this relapse was nipped in the bud. Baby Connor is healthy, safe, warm and well loved. This too shall pass. A few steps back is often part of a recovery journey and not the end of it.
I am hurting for you {{{{hugs}}}}