Not sure why you insist playing R&G. 22 games with R&G??? I mean I think even the team in England who set all lineups at the beginning of the season didn't play 22 times the same tactic.
The teams in your league look all very mediocre, more like D3 level than D2, including the guy in your conference who beat you twice and had a correct double GDP both times. GDP is part of the game and if you refuse to counter it by at least mixing 2 tactics, then you should at least build a team and use it to your advantage. For example, in D2 I have 78 OD in my PG+SG+SF plus my PF also has high OD: against good teams (and there are a few teams over 570k and 580k salary in my D2 league, that's 100k more than I have) I do GDP inside by default. I basically dare them to play something else other than LI and LP and if they do, I know I have more than enough OD for them to be miserable even with the missed GDP, not to mention that by playing outside or neutral they will get fewer rebounds and FTs.
We all play with the same GE. You had a slight advantage in that game (5.9 v 5.3 DMI, 381k v 372k salary) that basically vaporised with him using more effort. The injury did the rest.