A card like Midnight Sentry that provides a bonus to a card with a certain trait/keyword, do those affect themselves as well ?

Yes. Long as they have the trait they buff, they buff themselves as well.

Yes, it's what makes cards like Maester Aemon (core) quite a handy card in any deck. he can target himself to soak up military claim. When I first got the core set, I was thinking "argh, i know it's thematic but WHY is Aemon in this targaryen deck - he doesn't do anything!" How wrong I was.

so in reality, Hoster Tully starts at strength 1 then?

Mighty Jim said:

That is correct.