I wanted to re-publish this so everyone would see it.
Additional information and clarification below:
1) Form now can now drop all the way to 0, the new form range goes rom 0 to 100, up and down in increments of 5.
2) Players removed from the line-up have a higher chance of their form stabilizing or improving if they miss relevant games.
Sitting a player for a friendly will not affect form, but league matches, playoffs, playout matches, and national/nternational sanctioned in-game tournaments will.