Why give up on something as simple as this ?
Seriuosly, what's so difficult about this that you can't adjust the pointers correctly?
It could also be a problem of the used tool though but advancemap and xse should be quite stable as far as I know.
"Hm... Actually when I tried #dynamic 0x9000000, it just assigns everything to offset 0x10000001"
And, what you said here makes me wonder, was there even anything wrong with the dynamic pointers. Of course that address can't be 0x10000001 but 0x1000001 instead which is where pointer 01 00 00 09 (ram address 0x9000001) leads so I suppose that dynamic pointer there is working correctly.
Another problem could also be the fact that the game doesn't want you use to more space than there originally was. I haven't expanded the rom size of my silver hack (2MB to 4MB) because normal gameboy cartridges cannot handle that much data so a little bit of re-coding would be required. I don't think the same thing applies to your situation however.