1.- If powers in the tower are lent or granted by guardians, then the guardian wouldn't have lost to Enryu. He could just have stripped Enryu of any power.
2.- They climbed the tower with others because they needed them, and at some point there is nothing that prevents Zahard to have stolen other's powers and/or abilities.
3.- Zahard and Eduan are Data of the times when they cleared the Hell Train, not from they time they became FH, therefore they being surprised doesn't mean jack.
4.- Current Zahard wasn't even faced when Baam's Thorn activated spatial-distortion to save Baam, much less was he surprised by the fact that Baam was alive, in fact, he took it as another twist of fate for him to face, and even took the time to small talk with his data heavilly implying he had changed the further he got up into the tower.
5.- Current Zahard even admitted that he and Current Eduan are in bad terms and that both of them Data collaborating was a surprise.
6.- Whatever Enryu is or is not is not clear, so there is no way to pinpoint the origin of his powers, but it was stated that it was a Shinsoo fight and that Enryu did wipe the floor with the guardian without breaking a sweat.
7.- Me pointing that Enryu is not an Axis was just to indicate that Phantaminum is even on a higher level than Enryu, and of course even higher up than Guardians.
8.- So far, Baam is the only one we have seen to be able to absorb and/or replicate other people's skills and abilities, but that doesn't mean that he is the only in the tower with that power. After all, we are currently in the 52 floor (Correct me if wrong on this one).
9.- Yeah, you are right, there is a chance that Hana's flame have a different origin than evankhel's, but if evankhel brings up the subject of their origin and goes even further to compare her's to Hana's, gives plenty of room for speculation.