Are we supposed to have answers to the following questions?
When Admiral Bei says he's been communicating with the Vishnans in a manner he finds entirely unusual, are we to infer that he's just been receiving the same dream visions as his son? Didn't Sam say the Vishnans had no knowledge of his father until their contact?
Yep. Admiral Bei doesn't have the same destiny as his son, but the Vishnans do recognise him as a node around which great events take place and so begin communicating with him. This is a storyline which will be continued later on.
Also, it was reported that Sam's flightlogs from the First Contact mission reported no power drain, even though he reported one. What are we to make of this discrepancy?
Mainly that the Vishnans don't affect ships as such, but rather people's minds and perception. Everything that happened during the power drain was all in his head.
Lastly, the crewman named Eriana on the Sanctuary. Is she intended to be an alternate-universe counterpart to the Eriana killed in Capella?
Yes she is. It's part of Bei's destiny to
die, battle the demons of his past, and to be reborn anew, and in the process be given a second chance with his dead wife.
It also follows the New Age mythology that the souls of two soulmates ultimately travel the same path, no matter which life (or dimension) they inhabit.