Each MM has their own ask and bid - there isn't just one bid/ask. Different MM's may fill parts of your order. You'll get the best price available for each tranche...
That's why mm's spread changes - if they find they aren't getting the orders, they change their spread to start picking up more orders. It is an automated market, with computers keeping track of the rate of successful trades, and the spread may automatically adjust if they get out of range. Don't ever think people are watching these companies and manually adjusting things - there are rules for their computers, and they compete directly against each other, fighting to get the orders.
And again, MM's could care less what the share prices are doing - regardless of whether it is rising or falling, they get their spread and move on...except when a stock becomes illiquid, (no trades), upon which they trade amongst each other to keep the market fluid.