MR -The fact that they won’t help out is because they think a religious life is stupid.
Two suggestions that might sound harsh:
1. Go back to work and leave the kid by a babysitter, not a nanny (which is expensive), even if not ideal.
2. Minimize your Shaychus with them. You can get together for Yom Tovim and such, but avoid things like social visits and holidays that you might be invited for, eg. Thanksgiving.
They really don’t respect you or your way of life. You don’t have to seek revenge, but you don’t have to go out of your way to give them Kovod either.