He may be stronger with them, but take them away any he will become stronger without them. Harry needs to grow in strength. So take away support to make him grow and give it back in the end to make him even stronger after he has grown.
Agree to disagree. I think he grows way better with the support of his friends, otherwise he begins to wallow in arrogant self-pity.
Peak physical is where she was at in BG so no power up there. And Einherjar are not immortal, they died in PT and BG. Wereguild was paid for their deaths
Uh, not sure which two last books you read, but Murphy was
far from "peak physical condition", after the mauling she got from Nicodemus. Einherjar are immortal in the sense that they don't age anymore. Not immortal in the sense that they can't die again. Well, it seems, in the Dresden-verse. No guarantees that they are not able to come back again and again, like in the Magnus Chase books from Rick Riordan. We have no absolute certainty yet on how they function in the Dresden-verse.