Maybe Carter wins the debate, it was close until then. But most likely that's not enough. Eagle Claw succeeding seems implausible. No Volcker appointment I think would help as Volcker's shock therapy, while helpful in the long term, caused a recession in the short term and he was a nightmare for Carter. The Kennedy challenge and the dissatisfaction of the Democratic base hurt Carter too, the Democrats were divided and weak, there was widespread dissatisfaction with Carter in his base, they felt let down by and disappointed with Carter. A lot of people regarded the three candidates as virtually the same, in fact turnout in 1980 decreased from 1976(1980 turnout was at 52.6%), which was also regarded as an uninspiring choice. Fundamentally though Carter was almost certainly doomed given how his presidency had gone. So you would need to disqualify Reagan, maybe Carter wins the debates, gets a late release of the hostages or the
October Surprise conspiracy theory is true and is revealed to the public. I think the debate would be Carter's final chance, though Reagan would need to only do OK, as like Trump this year he had a lower bar to clear in that he just needed to prove he was not too extreme or dangerous. So let's say Reagan messes up the debate and Carter pulls a squeaker, maybe another factor put in there too.
The Democrats probably keep the Senate in this scenario given a lot of the races were quite close. However they will likely lose both houses in 1982. Carter has scored an upset re-election, but it was more a rejection of his opponent and still it was close. Congress is quite conservative, but he isn't very liberal. Carter's focus is probably to try and balance the budget, so no big tax cuts. The economy may be in recession for longer, perhaps this hurts Mondale in 1984. Carter may also try some kind of welfare reform. He never had a big agenda or vision though, that indeed was problematic for his presidency. He likely limps along, with a bit more of a hawkish foreign policy and no more detente but not nearly as much as Reagan. In 1984 a moderate Republican like Bush likely wins the nomination and the presidency and gets to oversee a growing economy and pass some tax cuts and all, but no conservative revolution under him. Alternatively, if the economy has recovered fully Mondale could possibly squeak a victory, though Al Gore lost during boom times, and then govern at least for one term and adopt a more liberal agenda, including perhaps universal healthcare or the like, though Congress is a problem. The Reagan Revolution is delayed but there still is a shift to the right and liberals are not that happy.