Yes, more generous to the passenger. If you fly on KLM, AF, LH or a USA airline they now decline EC261 protections on the basis that you are flying from one Third Country (India) to another Third Country (USA). The UK doesn't have a Third Country concept. Probably the most obscure bit of the sunlit uplands of Brexit, but there you go.

Yes you can ask to go Virgin or on another carrier, you should come prepared with the list of options that work for you. I'm just saying that if you went in blind on this, BA by default would offer an overnight stay. In other words if the robotics notice you can't make the connection, you will get automatically rebooked to first a BA and then another oneworld option on the App, and as mentioned in the link it's the App where you will notice this. You are certainly at liberty to ask for another option in BLR or LHR, so long as you don't accept the App's recommendation.

The wheelchair will unfortunately slow you down, no two ways about that. It will make it more likely you will end up overnight. But as I say, fear of missing connections is usually over played here, so I wouldn't worry. There are lots of services across the Atlantic and lots of domestic services to MIA.