2 things jump out to me and neither has much to do with his loan.
1. the notion of winter being bad time for sales is simply false in todays market in many areas. most of the areas where that is true it is climate related. hard to sell homes with a foot of snow on the ground. The market drives sales moreso than the seasons. Rates are super low right now, lenders aren't being as tight with qualifying credit scores, rents are high, it all adds up to homes being able to sell. You are at a higher price point which always takes longer to sell but when a home is in as great of condition as yours is and it's not selling, it's one thing and one thing only. Price. which brings me to #2.
2. If a realistic sales price is 750k, why did you initially list the property at 949k? I'm not local to your area but I can't imagine a million dollar home in So Cal NOT having a swimming pool. Seems to me that you were certainly priced way to high initially. Some people falsely think they must price high because everyone will be looking to offer low to begin with, but when you price it right from the get go, you generate the most exposure to your property and increase the chance of multiple offers coming in.
Finally, not trying to pick a fight but I find your attitude to be a bit offputting. "The area that I live in is referred to as "The IE" (inland empire). Think, flat billed baseball caps, sentences always completed by using the word "Bro", lifted 4x4 pickups that NEVER leave the pavement, tattoos, Harley Davidson, and very, very low IQ's. I almost forgot, smog and constant traffic congestion."
I don't wear baseball caps often but when I do, it just may be with a flat brim. I say "bro" at the end of sentences sometimes and dare I even say "homie"!!! No Harley for me but I do have a high end mountain bike. With all of that said, my IQ is 131. Not sure how you know these peoples IQ, or their income and if you are so intelligent, why did you choose to move there? I know plenty of wealthy people that are far from the smartest people I know. I know plenty of people in baggy jeans and flat brimmed caps on the weekends that wear suits to Wall St on the weekday. Your home is GORGEOUS. Everything about those pics says its an amazing house. The #1 driving factor in selling homes is price and yours is priced too high. If you listed it at 750k last summer when you first listed it, it would have probably sold by now. I think this guys offer is very reasonable considering the situation and lets face it, this is a negotiation, he isn't coming with his best offer because he knows you don't have anything else on the table right now. I think it's more than appropriate for you to counter with what you suggested and make it clear that you are open to doing what you have to do to make the transaction a win win for both parties. If you can't get a deal done with this guy, you should probably look to relist with a STRONG agent that will AGGRESSIVELY work to market and get your home sold. I'd be more than happy to refer you to a Keller Williams agent out there that would work aggressively to get your home sold. Inbox me if that is of interest to you.
You seem to have emotional reason moreso than financial reason to sell your home. nobody wants to lose money or not get top dollar but sometimes you can't put a price on your happiness and if you really want to get back to the Midwest, there may be a price you need to pay to do that. Don't rule that out.