Yes, and Yes. 1 person or 1 child, it's less than 5 people. assuming there's no other way to alter the conditions. The way the trolley problem is usually presented there isn't, which is significantly unlikely. You've got plenty of time to make the decision, but no time to contact the trolley itself, and no signals at the rails that could be changed. it's an unlikely scenario from poor design.

For 3, it's a definite no. pushing someone onto the tracks, or just into the way of the trolley isn't even in the same category of 'flipping the switch', it's straight out murder. The people on the tracks may or may not be aware of the oncoming vehicle, and could move without your knowledge.

Regarding the car, I would. It still comes down to numbers, and if I'm going to give up control of the vehicle, then it's similar to being in a car with someone else making the decisions, and they don't always make those decisions in your favour. You just need to see the safety record of passenger seats vs driver in accidents. And we have plenty of them. As the roads are more populated by automated vehicles talking to each other, we'll have less accidents. Then we can design the infrastructure to get people off the roads where they don't belong anyway.

No, I wouldn't. Safety sure, but not at all costs. This is what people already do, with the rise of the 4 wheel drive as a city car, because bigger is safer, ignoring that by putting more and more larger vehicles on the road, they actually get less safe because they hit each other, and those that aren't in the larger vehicles become less safe because instead of light injuries, they get significant ones, instead of significant injuries, they get critical ones... I'd rather we all drove small city cars and just had trucks as our 'large' vehicles to avoid, and ideally in the inner city, even they'd be smaller vans rather than big trucks.