You might look at other states' formulas for spousal support to get an idea of what's reasonable.
AS for buying him out of the house - some cautions for you. First of all - do not do that if you are not absolutely sure you will be able to pay for the house going forward.When you buy someone out of the housing equity you usually have to pay them half of the difference between the mortgage and the current value. This is actually unfair because it doesn't take into account selling costs, so if you were to have to sell the house a year later, you end up paying all the selling costs and getting less for your half than he did. Example: House worth $200k with a $100 k mortgage. You pay him $50k for his half of the equity, then quickly find you can't afford the house and have to sell it. You sell the house for $200k but have to pay 6% to the realtors and say $3k to fix it up for selling. So you only get $200k minus $100k mortgage balance minus $50k you paid to ex minus $12k to realtors minus $3k to fix up for sale = $35k. So he got $50k but you only got $35k. Even worse that you are "buying" it from him at the top of the market and the value might decline before you have to sell it. The worst case scenario is buying the WAS out of the house, then finding you can't keep up the payments and losing the house to bankruptcy.
Now, if you plan to live in that house for 20 years and you can easily afford it, great There's less disruption for you and your kids, and if you love your home and neighborhood, great. BUT if you really are not going to be able to afford to maintain this house and might be forced to sell in the next few years, you're better off to agree to sell it now, split the proceeds and buy a new less expensive home that you can really afford.
Look carefully at ALL the costs of home ownership, including insurance, property taxes, repairs, new roof, gardening expenses etc. before making a decision about keeping this house.
