Since he is grappled, does that mean Poljen's Disadvantage for attacks against him is voided by others having Advantage due to the grapple? I ask because then if he goes Reckless Attack, they still only get a normal roll against him, not with Advantage, right? And obviously he will only get a normal attack roll against the drake…
Indeed, if Poljen uses reckless attack, everyone will just be rolling normally.
As to Fay's sleep spell, yes you could get a fair number of them without including allies in the AOE.
However, in a situation like this, it is fairly safe to cast it right on top of your buddies if need be. 5E's version of the sleep spell affects those with the least HP first, and with all of the mooks on the field, will expend itself well before it gets around to affecting Targul or Poljen, even if you roll max.
Depending on how long it has been since Onwen cast False Life, that lightening strike may have dropped him to 0hp. If it has been less than an hour he would be at 1hp but if it has been more than an hour he is down.