The engine is trashed beyond repair - if you remove the gasket from the block and take a picture you will find that the block is eroded all the way to the cylinders - this happens when plain water is used as coolant forever - (evidence) - its not your fault either, the damage was already done way way before you added coolant.
To reface this engine, it will require welding to fill back the missing metal which is extremely expensive and then a reboring to oversize while perched on a crank jig rod like industrial diesels are bored (not block sitting on floor) - which again is very expensive.
It would be in best interest to buy a long block (assembly), tear it down and replace worn parts, check the timing slack etc. and repack it correctly with your old ancillaries and wiring before dropping it in.
After the job - the owner should be warned with instruction not to use "dumm ka paani coolant" no matter how convincing the sales pitch is.
