DID THE OP PUT ACID DOWN THE DIP TUBE? Its the pipe standing up in the
tank with a small water line running to it.....

pouring acid just in the tank will accomplish nothing the bowl rim
interior passages are what clogs.

if you flush every time with a bucket does the trouble disappear?

if so the interior passages are clogged.

while you had the toilet removed did you try dumping buckets of water
down the open drain line?

thats a important test to know if the problem is down stream