I'd tell your mom that in NJ and most other places the only assets that will be split are assets gained when married, ie assets that are a result of the marriage. A good way to look at this as an example is even if one works and the other stays home, that the one staying home is sacrificing their ability to earn while the other works, so half of the workers earned assets they are entitled to.

Inheritance doesn't fit into this at all, I would also make sure this is paid into a new account in his name only. Inheritance is an earning that your father would have received whether married or not. If the inheritance is solely his your mother has no claim. As your father has already offered $15k he needs to speak to a divorce attorney as that offer can be seen as binding.

As for the house and everything else, she is entitled to half not all of it. I think she's seen too many TV shows and has very unrealistic expectations of what she can actually get in court. She may actually get less if your father's attorney can convince a judge they have been separated but living in the same house for some time (unlikely) so any property value increase since separation she wouldn't be entitled to either.

For alimony, this depends entirely on earnings and who makes the most, if you have been living paycheck to paycheck, then you're looking at a very small alimony payment. By the sounds of it your mother can't make a claim she is used to $4,000 of disposable income each month. If you are a dependent and an adult of sound mind, divorce isn't may expertise but I guess you could choose to live with your father, this would offset alimony entirely and probably reduce your mom's share of any settlement as she would be the one expected to pay part of your care. Your testimony is irrelevant in anything else, but if you're legally capable of making your own decisions then it is entirely your choice who you live with.