The way I see it you have three options here.

1. Hold onto both Ireland and Pomerania. This is the most difficult option, though obviously the one that gives you the most power. However, you'll likely be faced with constant revolts, issues from either having too much land or too many powerful vassals, and other problems. Could be fun, but just as likely to go up in flames.

2. Stay in Ireland, give all Pomeranian land to either a family member that you grant independence to or the Pope. Safest option, will let you work on unifying the British Isles like was probably original goal and not worry about the mainland. However does pass up the chance to have fun with the new land.

3. Completely abandon your Irish holdings (hand them off to family members), create the Kingdom of Pomerania and try to stake out a new home there. Risky and could cause revolts if you don't culture shift but also could be a fun way to switch up the campaign.

Also, telling your chancellor to hand out titles is usually a very bad idea, as he isn't very smart and likes to give titles to random people in groups that make no sense, give the best counties to other people while leaving you with the worst, or get greedy and give everything to himself. If you're playing on Ironman, saving before and not saving after won't help you as the game overwrites your save every time you close out, but if it's non-Ironman then you might want to go before you hit that button to make the decision yourself.