...is there a way to explore all of Kenabres + Do all the companion sidequests, and still have time to strike at Gray Garrison before the Tavern gets attacked? Core difficulty and above btw, I would love to know the actual time limit in hours
You don't actually need to fully do Marketplace btw. The big timegated thing for Marketplace is:
1. Easier time killing your local inquisitor
2. Saving one of NPC for unlocking Azata without killing said local inquisitor without going full Angel option everytime by that point
3. One miniboss who will get replaced by another miniboss iirc
In general you can and want to avoid the mid section of the map with the Shades swarm and you will get easier time.