I can't see your win rate but your graph seems to be moving in the right direction and your red line also seems decent considering the amount of calling stations at the micros, so well done.
In my opinion yes TAG ABC play is the best approach for the levels you are currently playing at. Fancy play is wasted as majority of the player pool at 2NL are only thinking of what 2 cards they have in front of them.
As you start to move up a little higher in limits then slowly try and add in a few new things like light 3 and 4 betting, semi bluffing
your draws etc. Also when doing this you have to do it against the better players who are actually capable of thinking beyond what 2 cards they have in front of them.
35K hands is not the biggest of samples but it is pretty clear that you are beating the level and it is not just a heater.
I would suggest maybe posting some of your stats and also win rates by position so people can dig a little deeper and see if they can see if and where you could do with improving.