it sounds like you got a pretty diagnosis and some possible solutions.
what shoes you going to run in?
Dunno. Maybe Mizuno Elixir or 11m drop trail shoe?
new boost?
Something w 10mm drop. maybe even more for a while.
even with a "loose" achilles, haglunds deformity (bump on back of heel) will mean achilles gets irritated
easier than usual with flat/low shoes.
Also not sure where I can find flat trail, besides Chesboro canyon 1st 3 miles. Everything here is up and down.
Also going to sleep in the sexy boots amd stretch achilles/calf/posterior more.