Is there a maximum level for XP advancement & HP gain?
Not specifically. It's up to the GM. My personal preference is powerful but not superhuman PCs at high levels. However, since it's not an issue that I am currently facing I don't have a specific HP or level cap in mind.
I've also never had a game go beyond 7th or 8th level. ONce there are no more talent slots left, I start handing out in-world stuff that feels like getting a new talent (castles, minions, magic items etc.)