You need your own attorney and it may be unethical that this attorney attempted to represent both of you in the first place.

This whole situation is not uncommon in MS and the bankrupcy obviously plays a roll and there are likely to be more hidden reasons behind his generous offer.

While $1300 for child support may seem fair considering you are talking 50/ 50 parenting time it will end when the children reach majority, what about college? If you are on SSDI then then you have some income now and at 27 months you will become eligible for medicare which will not cover all your medical and Rx costs, something to consider is asking for him to provide a medicare gap & Rx plan, these costs are the main reason why so many marriages where on spouse has MS end in divorce unless they have very good medical insurance. If he won't continue your insurance, you possibly wouldn't have had MS without the birth of your children that he fathered, that would be a part of the ongoing spousal / child support costs and possibly some spousal support after the children reach majority. You are entitled to 1/2 his pension for the time you were married or something close to that in a buyout. Same thing for your share in other marital assets.
Just because you have MS shouldn't keep you from having custody or at least primary care since you have been the primary caretaker of your children.

True story.
A "friend" announced his wife of 15 years and of his 3 children had MS. This announcement envoked a lot of sympathy for him and his family, that was the public view. Privately he was soliciting favors from clients from everything from doing housekeeping and gardening, auto repairs, artwork, carpet cleaning and trying to get his wife's Rx filled on his client's HMO Rx plan! Unfortunately he was also soliciting "favors" from at least 5 of his female clients including having sexual encounters in his office which threatened his license. I had knowledge of many of these ethical/legal violations and was in a place where I had to cooporate with the professional board as a witness. About this time he became more open in a serious/sexual relationship with one of his borderline clients while billing her insurance company. Eventually he moven into an apartment with her while publically denying their relationship and accusing me of slander and blaming me for him getting caught, he is a self admitted narcissist so this was in character.

He filed for divorce without an attorney and stated on his divorce petition that he would pay for his wife's attorney if she needed one. She got one, pronto, he eagerly offered what seemed a very generous settlement, because he knew his license was about to be revoked and failed to disclose that information. Luckily, a little bird called her attorney and informed him of the pending administrative action against his license and how to get the formal accusation, which put a very large hitch in his plans. He eventually lost his license and his wife got a better settlement that she would have had had the other offer been accepted. This was in a nofault community property state.

Get your own attorney who will represent your interests and the interests of your children and don't listen to his threats.