Harry is like some parody of Tough Harry, On the Run...With 3 minutes left on the warp core breach clock he has a petulant tantrum, "I can't! It's not working. Why won't it work?!...But what really pissed me off was how he made their deaths all about him, he was clearly there so that e didn't have to be the one who made a bad mistake.
Technically, since there's no Tough Harry (stationary or running,) there can't be a parody of him. For what it's worth Fantasy Harry's backslapping ways are not manly, but conceled aggression, which fits bitter.
As for the failure for the new figures to work? Harry from the Ex-Past must have told Starfleet what happened, and in their review must have worked out what they believed to be the correct figures. It was genuinely surprising that the scheme failed to go through as planned. Kim instantly blaming himself is guilt. Possibly the writers meant for Kim, to have screwed it up because Kim is stupid. (Yes, Kim knows engineering and science, but that's only book smart, not street smart, thus it's actually stupid.) This attitude to Kim is especially likely since Tom Paris THE WRITER (aka the Godhead Incarnate) made a face to indicate reservations about the scheme. Unfortunately if Paris really knew the plan was going to fail, he was the stupid one for not really making the point. Best not to dwell on this aspect of the episode, eh?
As for the supposedly selfish motive of guilt, well, people's motives are always ambiguous that way. The only way to keep that smear off Kim is if he didn't feel any guilt. Which to be honest given the situtation would be kind of monstrous of him.
However, since the emotional climax of the story is when Kim "wins," and saves the ship and his arms go pumping and he cries yes, and since it's just an asshole salving his pride, then the episode must be shit. Well the wise and good may agree with you, but hoi polloi usually like Timeless, and think it's one of the best episodes. Possibly the very best even. How imperceptive of them.