I don't think he cares about the decreased lifestyle.
Of course not. He's got his head up his butt.
He will care, eventually. OW will care too.
Hiring an attorney will school you so you will know exactly what YOU will retain.
This is very important so that you do not allow WH to bully you into any agreement favorable to him.
sell the house and use the money to wine & dine the OW and purchase a new Harley Davidson and a new home for them
We've seen this scenario play out before. It was not pretty. A poster, Believer, was abandoned by her WH for a married OW. They spent all the retirement, the savings, the equity .... when the money ran out, OW returned to her husband. Party over. When that happened, WH came to Believer hat-in-hand and wanted her to take him back. She was by that time (around 2 years I think) not even remotely interested. He then killed himself. What a stupid waste. Adultery makes normal people stupid, mean, and then bad things happen.
Believer did not listen, did not properly protect herself. She endured numerous false recoveries .... and it turned out badly.
Protect yourself. If you do that, you may also protect the remaining love for your H should he ever return to his senses (in time).
Remember, as you protect yourself, you are also acting on behalf of your child.