Other than specific cards that have "Trample Over Planeswalkers", you won't take any excess damage dealt to a Planeswalker
Each has two modes to choose from, and some of those modes are decent to very, very good
Only if they target your opponent or their permanents
The Chaos Orb will cost you between 450 and 750 Euros, depending on its condition
By putting Memory Energy on Stoutland, you can use Lillipups Pickup attack to recur an Item, which is usually Devolution Spray
In decks with 3+ colors with +1/+1 counter synergies, it will be fairly easy to put three or four +1/+1 counters on a creature each turn, and you should really have a good double strike or lifelink creature around to benefit from the extra counters