To add to what Tribal said, I have actually seen quite a few reimancers reabsorb leftover res (after you factor in the rapid decay of res after its creation of course) but I do not remember any founders including Tarot saying whether or not that was a legitimate thing. Its been done ICly, but multiple people, thats about all I can say on that and personally I do not typically do this as it feels a little wrong to me. Keep in mind its pretty rare there is any res left over to reabsorb anyway, given how quickly it decays and how much is used in actual spell casting.
Reimancy I do believe can be tied to emotions, depending on how the individual personally experience the magic themselves. Evalin for example is a very emotional character and uses those emotions to understand her own reimancy, and it has been a driving factor in her growth as a character. As far as self initiating with extreme emotions or trauma, that is a definite no. Reimancy has a specific initiation process that is etched in stone, and you have to be aware and accepting of it to really work right because there is a decent chance the initiation will kill you.
Again just echoing Tribal on most points I hope this helps