Reply to "R12 capacity"

Yes there are some discrepancies in that link.
I presume you are using the original compressor pump. It would be best to empty out any oil you have in it and replace with new oil. Hopefully you replaced the filter dryer and put in a high / low pressure switch. It is also recommended to replace the expansion valve.
The best way is to vac the system for ~30 mins. Switch off vac pump and check after a while you are not loosing any vacuum.

If you have access to nitrogen you could pressurize the system with that to check if you have leaks. It is cheaper and not as nasty it does leak.
Just dont run the compressor with the nitrogen.

Not sure how much oil you need to add for the original compressor, but if the dryer is replaced and the compressor is emptied you can treat as a new fill with oil, otherwise you might under or overfill with oil.
You can start with 1.5lbs of R12 + oil with the engine off and go from there. Then start the car. You really need to use gauges and temp gauge /gauges to put the correct amount of gas in. Here is a link to general guide on charging your system. A/C guide
I just charged mine over the weekend. R134A, all new hoses-dryer-expansion valve-Sanden rotary pump-trinary switch with front condenser, original evaporator etc. Used most likely less than 2 lbs in the end and got 32 degrees F at the vent with ambient at ~90 degrees F. Very pleased.
Good luck.