Hi pinkbuttons, been following this thread & I'm sorry to hear about what's been happening to you these few months.
I guess it's too late to feel regretful about the issuance of lawyer letter to your hubby. Though I personally find it nothing wrong as your several appeals to him previously have been to no avail. So I can understand the frustrations & unjust in you. When we think that he's a such a weakling (or maybe only to his mum), he actually fights back.. and retaliates by seeking legal advice (that's if we're not wrong). Seems like he doesn't remember how much you have helped him before financially & how much you have suffered due to his monstrous mum. He doesn't realise that he's failed to fulfill his responsibilities in being a good husband. If he does, upon receiving the lawyer letter, he would have also talked to you privately to know what's going on, in the hope that you would revoke your request, or best to improve the situation.
However, like others have said, it's very difficult to quantify the scope of assistance you've given him in monetary terms. Even if you have kept all the cheque butts or bank statements, it's still arguable if he's out to turn the table. But you have to know what you really want at the end of this divorce path. If freedom (esp free from misery as a result of all these mistreatments & stress from your MIL) is what you want ultimately, be prepared to lose in some ways.. if you manage to recover some parts of the monies you loan him, that'll be a bonus. In a sad way, the more he repels, the more you would feel relieve as can you imagine, he could be way too unreasonably & foolishly submit to his mum, yet has the heart to fight against you. You should know by then where you stand in his heart.
On the other hand, your lawyer, with years of experience, should anticipate this kind of response from your hubby and he should be giving you sound advices that can try to put you on the upper hand. A good lawyer does not only act according to clients' instructions, but also to advise them the best actions to take so that the possibility of being at the losing end is reduced to the minimum.
Please bear in mind that the longer or the more you fight, the more legal fees you'll incur.