On taxes: This was my offer to H year before last: I would figure my taxes in the way most advantageous to me. Then I would figure them jointly, and H could file that way as long as I got the same as I was getting alone. For example: If alone I got a $2000 refund, then jointly we got a $2500 refund, I'd still get 2k and he'd get $500. If jointly we only got $1500, then he could pay me the additional $500, which would still be far less than the 4000 he'd owe filing separately with no deductions. Either way I came out the same and if I could help him out, that's fine too. However, I respect what you said about setting boundaries, and it really might be best to set them early on.
As logical as my offer sounds, it didn't work out for us. Our draft separation agreement said we'd file jointly if "advantageous to both parties". I correctly interpreted this as being if it worked out best for both we'd file jointly, but if another way was better, one could opt out. H insisted it was what's best for BOTH of us (meaning him). We exchanged several nasty emails before I just gave up and lost about $700. Last year I didn't make the same offer, he hadn't changed his deductions, and ended up owing several thousand dollars. His poor planning was not my problem.
On the custody: does your W really want to be able to come to an agreement between yourselves? It's not possible to tell that from what she wrote. She states you can't, but doesn't say she wishes you could.
