I'm looking to install a Schneider surge protector at the main breaker, likely this one: https://www.amazon.com/gp/product/B00CONA1OQ/
The key things in the instructions which I'm trying to resolve:
Install it as close to the top (main feed) of the panel as possible
Use an empty 20A 240V breaker
In some jurisdictions (I'm in FL) you can piggyback it onto a used breaker by wiring it in the same hole as the existing wiring, but otherwise, you can consider adding a new breaker.
So, my questions:
The breakers at the top are 60A, will it matter if I use one of these?
If I do, can I piggyback it in with the wires in that 60A breaker?
It looks like there's a spare 30A breaker near the bottom. Does that look right? If so, will it matter that it's not 20A, and also that it's not closer to the feed?
Is adding a new breaker at the bottom feasible?
I have an older house which doesn't have grounding throughout, and I'm wanting to put some surge protection in. I've read mixed info on whether a ground is required for surge protection at each socket, and in the end decided it's just going to be easier to do it at the main breaker.