I have run a WWA Mini kit on a full bodies karni, so I'm surprised it didn't work for a mini. Please note that because of the karni's milling, the pump kit is able to wobble side to side (Karni has a round body, where standard has a rectangle body. To stop this, use teflon tape or loc-tite. Otherwise, it could be a problem with the threading of the front block when the karni was cut down.
you should just post up a full pic of your gun/ the individual parts so we can see what the damage is. we can probably address some of the problems better. IMO the poump kit you have may be salvagable if sent to a machinist