It's harder if you are higher level...
I recommend going to chapter 1. Unknown dword. Kill one zombie. Unknown changed. Search 0x4. Kill the next zombie. Unknown changed. Search 0x4. Then like item qty, look for 2 values when subtracted = xp. You'll have to guess what looks right. So obviously if you see a value that is like 10, and you are level 15, you obviously have more xp than that.
Xp DOES NOT have an id pointer. I can try to browser memory structure, and see if I can pinpoint xp in memory without knowing the value at all.