Forgive my ignorance or temporary brain fog, what does PG mean when you say made it for your PG?

The main thing is to treat domain powers as their most similar spell and level they are received at for spell level.

Breaking it down(only things that add ego)
12 INT, +1 ego
16 CHA, +3 ego
Telepathy, +1 ego
Grease(1st level spell) 3/day, +1 ego
Weapon cost: +2 is 8K, returning is +1 for a +3 for 18K, 3K for adamantine so 21K plus hammer. +4 ego


So that's 10 ego right there.

The first power of the weather domain is efectively 3/day 1st level SLA, so I would rate that as +1 ego.
The 2nd level is effectively call lightning, a 3rd level spell. The spell is 1 min/level, but it really only allows for 1 bolt per level, effectively casting the spell once a day. +1 ego.

So your total ego for the item should be 12.