To answer your questions...
1: I wouldn't bother unless you want a more modern WAP with Wireless-AC and such.
2: Wouldn't hurt to get everything IPv6 compliant.
3: Remote access via IPv4 isn't possible, and remote access via IPv6 is a nightmare at best.
4: Wont work on Hughesnet over IPv4.
5: Remote access in general isn't possible with Hughesnet Residential services.
You may want to review the following topics.
https://community.hughesnet.com/t5/Tech-Support/HT2000W-IPv6-inbound-services/m-p/83342#M58814
https://community.hughesnet.com/t5/Tech-Support/Remote-access-of-security-cameras-REVISITED/m-p/84688#M59728
Only way remote cameras work is if they are cloud based, not peer-to-peer address based. I have two Nest cameras which are cloud based and they work fine. Even so, can't leave them on 24/7 as monthly data will be consumed in a matter of days, if not hours, depending on the definition camera is set to and the movement in the room.
