I'm about 2100 (much weaker than IM) and from the looks of those games I would have easily won with the same handicap vs. durr. What a great bet lol.
As far as various handicaps, a GM would beat almost any basic master with pawn odds, much more so a weaker player.
A decent club strength player should be able to win with rook odds most of the time, and piece odds would be close.
Somehow the games felt tougher than they may have seemed. durrr never flat out gave away material in one move and seemed to be working very hard. A lot of his moves lacked any chess understanding but I did feel like I had to calculate some stuff a few times and that if I made a careless mistake he was capable of picking up on it. I mean the first game was actually pretty competitive until he played ....Kf7 on like move 25-30. Despite that ok I'd probably win starting with 2 minutes on my clock, but it'd be a lot closer.