D&D 5E Help me pick my next level (and feat)!

[Shallown]

I would go for spell penetration. You have plenty of in character reason's why between demons trying to be your friends and the things you have encountered recently.

If you Do spell thematics I would go for more alienest looking magic. Magic missiles that are squigle worms and Fireballs being hot flaming masses of tentacles. etc.

I would also go for a wizard level. Nothing like going back to basics especially considering recent events.

Just a few Ideas. I don't think any PrC's are appropriate in present situation and the ones you have are fine like they are.

Later

 

[Lord Pendragon]

Well, others have talked about various power choices, but one that might be fun is to take a level of wizard, and then the feat Extra Familiar. Proty's already amoeba-like. You could have him "split" and form a second familiar.