As I mentioned before, the Allies had the point, at which they could decide to make peace. The chose for war. And as I mentioned before, it is very hard to correct such a move. Heck, even if they did so at first, it would be a problem for them, as they had forced them to tell their electors, why this was now a better action. In one moment it was "unconditional surrender" and in the next "okay, we make peace talks".
That having said, the personalities of the leading politicians are a problem as well. Churchill was in some points a gambler, Roosevelt hated Germany and Stalin wanted to use an opportunity. IMO Roosevelt would be the very last to accept peace talks, not, if he doesn't see any possibility to win. His personality and his point of view on Germany make it harder to change the longer the war goes. That and the fact not having lost the first war in the history of the USA. Churchill, if really free to act, would have acted otherwise. But as a gambler he can live with it, as it would mean winning the greatest jackpot in history.
Stalin was very cautious. Thus he would make peace, once there is a danger to his rule. OTL he sent whole armies into doom and would do so here, if he could get a possibility to win. OTOH he would make peace, if he sees, continuing the war would endanger his rule.
None of the leaders of ww2 really cared about the population or the soldiers.
Stalin was cautious, but beliver - that is why he planned to start WW3 in OTL.He would do the same again here.Becouse he really belived in "liberating " entire Earth.
Churchill in OTL did what USA told him,so he would again do that.
FDR was feeling bad,so more important were was his advisors would say to him.Considering that such advisors was Stalin creatures, they would urge him to fight only if Stalin want so.
And your basic mistake is gathering germans 44,germans 2015 and germans from USA 2015 in one country.
1,they would need food - which mean,that they must steal food from occupied countries.
2 - american from 2015 are loyal to USA,not Germany.
3.Germans from 44 are genociders at worst,and best - like Stauffenberg - had not problem with german Ju 87 destroing polish city Wieluń in 1939 when there were no polis troops there.They targeted hospital with red cross on the roof,too.
He "only" want use Poles as slaves on their own land without killing them.
Well,there were people like mystic Teresa Neumann,but she farsee germany destroyed for their sins in WW3.
And till beginning of 1945 they were loyal to Hitler - otherwise soldiers facing allies would just surrender.Just like Italian troops in 1943.
So, we have starving country with 3 mixed population,and only germans from 2015 are loyal to Merkel.SS in OTL supported Hitler till the end - and they have 38 dyvisions.Wermacht,except higher commanders, was loyal,too - otherwise putch would succed in OTL.
If story was real,we would have cyvil war in Germany arleady.And starving any occupied nations.