1) to be cleared dream state requires that you own 30+ chakra when the cleaning effect is applied.

What actually debuff immunity suppression does is to deny the ability ninjas have to selfclear debuff before each action until the end of the round (basically they continously cast on themselves the same thing as nagato passive) so if at the end of the round your team do not own 30+ chakra the effect will stay for the begging of round 2.

On paper if you do not use chakra asap in round 2 and the enemy doesn't steal your chakra with his action then the ninja should wake up after the enemy uses his 1st mystery or standard attack, but not before, because before the enemy ninja action the passive effect of the full immune ninja would clear again the debuffs and at that point you would own 40 chakra, but i am not sure if this actually happens since it never happened to me to find myself in that specific situation (using kushina and itachi together generally makes no sense in our current meta). Theoretically should work so (the full immune ninja should basically lose the chance to use the mystery before the enemy moves, basically).

2) this happens only for ninjas with a single target standard attack. For the other ninjas chaos isn't different from immobile + blind.

3) in sosp case isn't possible for the reason i said in 2, but in general what chaos do is to let the enemy use his standard attack, but only for the damage side. While chaosed his combo rate becomes 0 so it's impossible to trigger any effect linked to combo (exactly as you won't start a chase because the standard attack won't trigger knockdown or repulse it won't trigger neither other effects linked to combo, like mystery cd reduction, but will apply effect linked to the damage, like poison tai).

4) ninja tools, runes, refinements but beware owning initiative if you don't own attack/ninjutsu/injury/critical is quite pointless.

5) the team kushina habanero, iruka, gaara kk, earth main all full sb is currently the strongest team you can get for less than 35k coupons. Basically kushina habanero is the answer. Iruka, gaara and earth main are there just to let her survive and stack a lot.

Besides her, your second best option is edo minato. A team like edo minato sage naruto edo roshi wind main with a bunch of sbs on edo roshi and naruto and the main sbs on minato is quite competitive and isn't excessively expensive.

The third best option is hashirama 1st hokage with chojuro and mifune, all of them full sb, with water, earth or lightning main.

6) training potions > mt.myoboku>summon cultivation/charms