1992 Toyota Pickup a/c system

Old R-12 system had leaked out/stopped cooling, and a mechanic friend (who admitted not knowing about a/c systems), said I could just add R-134a which did not hold the charge (get cold) for over 2 days. I purchased a stop-leak product and wanted to install myself, but he jumped in to do it before I could (he did not read about anything first, not even instructions on the product!). I did much research and learning at that point. Bought gauges, pump, etc.,

Replaced lines/hoses (except high side), accumulator, expansion valve, condenser, compressor, radiator/hoses, and put back together. Flushed (old radiator prior to removal) and filled new on after installing with 45/55 distilled water/toyota recommended coolant then made certain that all ran fine. Drew down system and it held overnight. Added freon, compressor engaged, but I did not use the gauge to add because the can did not fit the yellow hose (still do not know why new hose does not fit the cans). Used a device to do this that auto-checks system. A/c did not get cold. Evacuated system again and started over. Now the a/c compressor does not engage. I know at one point I must have overcharged the system, but I let the Envirosafe 134a out to relieve pressure.

I did forget to start the engine before trying to add freon the next time and had someone do it while I had the lines connected. Did I damage my new compressor? What other things could be wrong?