Ok, understand that he is either irrational or getting bad advice. If he were getting good advice and he really wanted the children 50% of the time, he'd be taking them now. Document when he has the kids and when he doesn't. Understand that this won't matter at all, but it will help you counter his claims that he's tried to see them.
What your lawyer has suggested is likely done to make him seem unreasonable. I'm guessing that you've suggested numerous solutions (with written proof) and haven't gotten back viable alternatives. It's likely your lawyer is at the end of their rope and if they know the judge and the legal system in their state, they likely believe the courts will be on your side.
Now, take a deep breathe and make sure you understand what you really want. Write up your parenting time proposals and have a few versions ready to provide your lawyer, and know your limits. A judge will not give X custody when he can't care for his children (nor will a judge allow a girlfriend to do it - typically).
CS is calculated by formula in many states, that usually takes it off the negotiating board. My agreement says that we split work related childcare based on our incomes (and keep this outside of the CS calculation). I have in my docs the "Right of First Refusal" meaning that you first ask the X before you get another caregiver (for more than 2 hours). If you include a childcare stipulation, he'd either have to watch the kids or pay a portion for their care. So that problem is solved.
Now, relax because many parents play these games, including my X. It's really all about you and not about the kids. Do what you think is best (and realistic) for your kids, knowing that they need their father in their lives. Ask your lawyer what is standard in your state and understand that there really is no standard these days. My state is moving more toward 50/50. When my X fought it, he actually got less than I was willing to give. Just so you know, my X has not taken 1 hour of offered time, not has he wanted to make up any time of his I took for Mother's Day or other holidays.
If he is going to be difficult on this, I also suggest that you put in a stipulation about sharing costs for counseling for divorce Adjustment for the kids. They may need this. Also look into a kids support group in your area
www.rainbows.org these are really great for everyone.
The book Mom's House/Dad's House has some great parenting plan examples in it.