Did I mention, I'm known as....Lefty!?
j/k!
I'm very careful when working around any sort of machinery. I've worked on/around cars my entire adult life. Working around any moving/spinning metal things can be dangerous, but as with most things, a bit of caution, along with some (un)common sense goes a long way.
BTW, I don't clean my spoked wheels that way. I just turn the wheel by hand for that.
As far as starting the engine, why not? The bike's not going anywhere as long as it's already balanced on the jack. One certainly doesn't want to rev it to redline time after time, but idling or mild steady throttle works fine. Just don't get it to rocking back and forth!