You might be better off to post your questions in the Enderal section, perhaps in the Discussion heading. I don't know how many people read the "small talk". Although the forum isn't too lively at the moment.
Re Affinities, mostly what you get is a boost in certain skills, and you can boost those with skill books and armor bonuses, so nice but not too critical. I wasn't too impressed with the special talent you get from affinities. Others will probably differ, but for me, I found it inconvenient to use a quick slot for something that didn't work too well for me. In my case:
Arcane Archer
Boosts Archery, Elementalism and Light Magic.
An arrow fired during the effect of "Eye of the Storm" will be followed up by a Spectral Arrow which briefly paralyzes the target.
I didn't care much for Eye of the Storm and I felt it was a waste of a quick slot for that, as the Spectral Arrow didn't do that much.
So if you feel what you are doing is "pretty good" you should probably stick with it and not mess around just to try to get an affinity. I can't offer any advice on the 3 disciplines you use as I don't use any of those 3. However, the Devs try hard to get everything balanced so that you pretty much can't go wrong with any of the disciplines.