1. My FPS are relatively low when I look in some directions in Pell's Gate, but nothing serious (and in most places it's fine anyway). Overall I think the framerate is acceptable - and I'm very picky about framerates since some mods don't seem to care at all for it. I don't run any texture packs, but I have a few NPCs added by other mods passing through the town from time to time which might decrease performance. Just yesterday I saw a merchant with his guard followed by an adventurer passing through, all of them riding a horse. That's 3 NPCs and 3 creatures more than planned and the framerate was still acceptable.
2. The Lost Spires patch will be a bit tricky to make. I know of at least one scripted sequence that takes place in front of the Archeology guild and there are lots of persistent references added by Lost Spires where Pell's Gate is. Since these references are stored in the save game and since AI packages and possibly scripts refer to them it will be hard to move them. I think you should get help from an experienced patch modder to figure out if and how it's possible.
3. I could need some help with the gallery quest. I should probably look a bit further before I cry for help, but I'd like to go on since my time is limited right now

4. I found a bug that was most likely fixed already by the patch you released. Didn't play with the patch yet, so I just mention it anyway.