I’m not familiar with the track there, but it looks like you are VERY low on entry to some of those corners. It also looks like you aren’t pushing very hard. If I may ask, how far are your times off the leaders?
The reason I ask is because it doesn’t look like push-kick that you are experiencing. It looks like you aren’t on the limit that the kart requires to work and flex properly.
Also, it’s basically impossible to try and tune a kart on old worn out tires. It isn’t going to react the way it’s supposed to on old rubber.
First thing I would do if you want to attempt to fix the oversteer, is to narrow the rear by 5mm each side and see if you can get the outside rear tire to dig harder. But my gut feeling is once you switch to a fresher set of MG Yellows, it will completely change the kart. My advice would be to leave it at a standard neutral setup and put the new tires on and see what it does first and go from there. Depending on temperature, probably aim for 9-11 on tire pressure at 405 pounds on Yellows.