If your son doesn't like the atmosphere in your house, then that's a good incentive for him to reach an important developmental milestone: getting out on his own.

You can't afford to do a downpayment on an apartment for your son. That would not be "helping" him. At age 27, he can work and save up for that on his own. He needs to learn to take care of himself, so he doesn't end up like your boyfriend.

The money that you have is for you to hold onto for when you have an emergency. Your responsibility is to take care of you and maintain your house. Let boyfriend and son be responsible for themselves.