How early should we show up before the performance starts?

Once the door closed .you will need to wait at least 10 minutes to get in

Yep. 45 sounds about right.

I agree l, at the very minimum 30 min, but 45 to be safe as well as be able to look at the merchandise, etc. We planned for 30 and with parking etc just barely made it in.

I would give it at least 45 min to locate parking & walk to the venue. You won't be allowed to enter once the production begins & will have to wait until intermission to be seated.

For Hamilton? I'd say at least 30 minutes