1- there is one or more Nash equilibriums to poker NLHE 6max and full ring. This is proven by Nash theorem and is explained here: https://www.cs.ubc.ca/~jiang/papers/NashReport.pdf
2- A Nash equilibrium is precisely a point where if both players know exactly the strategy of the other player, there is no way to exploit, ie deviate and benefit from it.
3- This has been found and solved for heads-up limit poker.
4- It has been proven to be unsolvable with computing power as we know it in our known universe for no limit due to the number of decision points. Same as Go which we can't solve.
5- Both Libratus and Cepheus have algorithms converging to Nash equilibrium for heads up nlhe. And have had trials with humans that they beat.
6- Pluribus has not been proven to converge to Nash equilibrium, it does reduce exploitability with each "learning cycle" though. And did reach algos where it statistically beats real top pros.
7- Pluribus does not attempt to reduce variance and as such assumes infinite bankroll. IE in real life it would go bankrupt pretty often before winning big money. In the highly publicised match again,st pros, it did lose 70K$ actually.