Make sure whatever you try next is more T shaped than what you just tried.
You've got a classic case of chafing (butt/ham crease) that screams "too wedged!" and sliding back on the saddle could well be an attempt to get a bit more landscape for the sits and to get away from that too-gradual transition.
The inner thigh chafing could be from a nose that is too wide, or a side effect of trying to clear your hip joints by shifting backwards (so the inner thighs rub on the transition zone).
You could have a saddle that's perfect in every way: wide enough for your sits, minimally padded or cut-out enough for your bits, and at the perfect height and tilt... but if that transition from sit-to-nose is too gradual for your hip joint motion, it's all over! You'll chafe, you'll squish, and you'll shift around all the time.
If anyone ever comes up with a short-cut test to figure out if one needs a T or a pear/wedge saddle, please let me know. All I know is trial and error.
"If Americans want to live the American Dream, they should go to Denmark." - Richard Wilkinson