428 or 520?

[Oldwolf]

Bike = happiness!!!

So, my brozz just turned over 700 miles most of which was on the road. Which is exactly opposite of what I had planned. (Better, but diffrent) So the new plan is to drop a tooth in the front get that extra 5 MPHs so I can cruise comfortably at 60. As long as I'm going in I figure ill upgrade both sprockets and the chain. Which leads to today's questions:

Is there room on the brozz to run a 520 chain?
Is there any downside to running a bigger chain?
Tensile strength, if I get parts way stronger than what is required will it last a longer time or cause issues?
If I do stay with the 428 can I reuse the chain? Chain was updated earlier and has about 200 miles on it.

Thanks gang!