You can check wear of the complete clutch pack by measuring total thickness, for a standard clutch pack I believe this is 1.4”. I’m not sure what it is for a 7 plate but @TR7RVMan
Don will confirm. You can then compensate to a certain extent for wear by increasing pressure on the springs by further tightening of the nuts.
Those brass hex drive clutch spring adjusters, while being very pretty, are not going to allow correct adjustment of spring tension. In fact I think this is probably your problem.
Correct tension of springs is likely to be achieved with the end of the bolt somewhere between bottom and top of the slot in the standard nut. But these hex drive nuts will not allow this as the bolt will force the allen key out of its hex.
So I would suggest:
Clean everything up, don’t do any more scoring.
Either source a set of standard slotted nuts or cut a slot in your brass ones so they can be tightened with a screwdriver, you will need to buy the tool or make one with a gap to clear the thread of the screw.
Reassemble and tighten till the screw thread is flush with the top of the nut. (Looks to me like this will be several turns more than the amount of compression in your pics). From memory this is how my 7 plate is set up, pull is easy enough for 2 (arthritic) finger actuation and it does not slip.
Check the pushrod adjustment again with the cable disconnected. Check you can still pull the clutch ok and if so test it for slipping.
It would be good to know what springs you have in there, normal practice is to fit 650 springs with the 7 plate but there are several variants, some of them too weak. There is a table on here, posted in my “Heavy Clutch and Reluctance to Change Gear” thread, with dimensions of the various available springs, length, wire thickness and number of coils. My bike came to me fitted with 750 springs so strong I couldn’t pull the lever. The correct 650 springs, adjust to Don’s method fixed this without slip.