I don't know if scrolls stop working when I don't have mana -- I've never had the opportunity to try. Then again, I don't think I remember scrolls using up mana, so maybe they'd have worked. Then again, maybe another spell was cast on you that would have stopped that scroll (or maybe other scrolls) from working.

I hope I'm not out of line for saying: the refresh potions I've run across mostly just restore movement, and not mana. And, not a lot of movement, just a little. There's probably others, though.

If you can't get things out of your backpack (this is slightly risky, but just about everything is), one thing you can do is drop *everything*, including the stuff you're wearing -- then you might be able to get something out of the backpack. What you're wearing counts towards your limits of what you can carry.

Finally, a help file you probably want to read (not just the bit about strength, but the part about dexterity):

http://arkham.carrionfields.com/display.html?hid=225&osea=stats