The first thing you should check when you have brine push is a blocked drain line. Do you get adequate flow to the drain line?
I doubt this is your problem but an excessively high drain line, or low water pressure and a raised drain line can combine to create the problem you are describing. You didnt mention drain flow, so I thought I would start there.
If you have water flow to the house with the softener in service, you should not have a problem with the tank, bad resin would typically manifest itself as no water pressure to the house.
Keep posting information, we will get it fxed. The Clack valve is fairly bulletproof, and a proper rebuild will usually get it working as good as new.