Rules

Gritty Healing and recovery
Dropping to 0 Hit Points

Add "Regaining Hit Points: When a character that has been dropped to 0 Hit Points and regains hit points that character gains 1 level of exhaustion unless you are already at maximum exhaustion."

Short Rest: Can spend 1 hit dice to remove one level of exhaustion. A short rest can be a small as 20 minutes.

Long Rest: Remove "At the end of a long rest, a character regains all lost hit points." Basically they get all their hit die and remove 2 levels of exhaustion.

Partial Recovery If the quality of the long rest is poor or interrupted the GM can rule that only half (round down) of the hit dice/spells/exhaustion levels are recovered. If it is really poor none are recovered.

Wands
You are limited to 2 extra charges when using extra charges with wands.

Grappling, Shoving
Add +4 to the atheltics skill for each size class larger you are than your opponent

Add +4 to the acrobatics skill for each size class smaller you are than your opponent

Add +4 to avoid being shoved if you have 4 or more legs.

You can't grapple a creature that is 2 or more size classes larger than you. If you try all you are really doing is choosing to hold them. They are not slowed by you and can move normally. You are moved by them.

Polymorphing
Wild shaped and polymorphed creatures retain their feats and skills if they are accustomed to their current form. Don't do this for abilities that are clearly tied to the shape of the creature.

Wild shaped driuds can still talk while shapechanged, though their voice is limited by their form. (GM note this not about balance merely playability, forcing a character to regularily not talk for extended periods is bad for the game)