I actually got a lot of my ideas from reading about Tocharian. The role of ə specifically, as will be expanded upon soon, was shamelessly stolen straight from there.
Yes, that's the outcome of the palatalisation, with ś coming via ź, with the same development of the aspiratae to fricatives as Italic.
In regards to accent, I'm a little torn as to exactly what to do. Having read many of Kloekhorst's articles on the accent-ablaut system, I've been forced to abandon some notions, while others are essentially confirmed. The only differences I have in opinion with Kloekhorst are (as always) in the specifics. The options are mostly where down his proposed line of development in the accentual system to break off. Methinat has always been roughly contemporary to Anatolian (in terms of detaching from the family) so it's reasonable that the inherited systems will be similar. Or, I could make Methinat even earlier than Anatolian, in which case I could just straight-up start from the primordial system with no additional changes. But that then adds the problem of assigning lexemes to this system.
That sounds wonderful! I always like to cross-reference the dictionaries I have with one-another, to see where the authors agree and disagree with each other. It's far more enlightening than just being exposed to one viewpoint. I also plan on using said dictionaries to make my own PIE lexicon, mostly for conlanging purposes.