I mean, the game literally tells you,
that entering the Shadowfell in the Gauntlet is a point of no return. If you knew, Halsin is waiting at the shore, why do you go along, doing stuff, that literally tells you, from here on forward, there is no doing sidequests anymore?
You blame the game for stuff, that you messed up and then complain, that the game hits you with consequences. That is like putting your hand into a burning fire and then blaming the fire for your action.
But if you don't like games like this, move on, I guess. Don't know, what you even want to hear here.
Zenith above gave you dome tips how to deal with the situation. So if you want to give the game another chance, go back before the said point of no return, rest, switch maybe some spells around and then the Halsin quest is not that hard.
Btw, you can heal the portal.
