Player form itself is generated randomly based on very weak rules. Weak here mean it satisfies some "actions" carried out by player on the pitch, but at the same time does not do justice to "key actions"

Let me explain a simple example:
A striker scores a goal and misses 8 chances. Half the time, he'll be rated 6 by the game engine. He is penalised for his misses but is not credited for the goal which in some cases, are winners.

A midfielder does nothing to the team, but does not do anything wrong either. He doesn't score, doesn't assist and his average rating for the season is 7. He gets a 7 because he did not do anything wrong in the game engine's eyes.

OK so I've got that over with to set some expectations. To answer your questions:-

What is the best way to get a player back to form?
This is vague, a lot of ppl will tell you 100% condition, 100% morale, win bonuses. But this is crap. This is more of a hidden programming attribute that certain players will go on a downward spiral until he changes teams or if you are lucky, he sits out 4-5 matches or even the whole season. Also, the simplest way to try to get a player (not team) to return to form is to switch sides (as mentioned by someone). If you play two strikers - switch. If that doesn't work, play lone striker.

Why is bad form affecting most of my team?
A wild guess, most your players are from the auction list and they all perform well together at one point and suddenly decides to not play at the same time as well. This is a regular phenomenon by players bought from the auction list. There is no logic to this. This is part of the game which is to "push" you to sell and buy new players. Also, it could be you brought in a new mediocre player and somehow the team chemistry (game calculation) is skewed from good to bad. I've sold some of these players jst to get my team form back.

Is this a cycle thing that will correct itself?
As I mentioned above, the cycle will correct itself for a few select players, but some players just continue to not do anything for you on the pitch and do more harm than good.

Is there ANY information on Form, I can find nothing in all these posts.
There is NONE