Obsessing over my AC 134 conversion

[PbFut]

Those of you that have read my past post by now know I tend to obsess over stupid little things. It’s a bad habit but like an itch difficult (for me) to satisfy. I’ve never performed service on a AC before so I’ve been reading up. I have a couple simple questions I can’t find a definitive answer for.
Key points. The system is an original 1972 R12. Air handler fan and vents clean and heater works very well and blows hard. I will be verifying the POA valve is working and recalibrate to the recommended pressure. I will retro in a parallel flow condenser. A replacement original style compressor (4 Seasons) will be used and says it has the correct 134 compatible oil in it. Dryer is replaced. Soft lines replaced. Hard lines cleaned. The evaporator flushed as best I can while in its installed position. I found zero contamination in any part of the system.
Questions:
1) Assuming I got all the old oil out of the evaporator and other lines, dryer, and condenser will be new, how much more oil will be required?
2) How much 134 will be needed for an empty system assuming the parallel condenser is roughly the same capacity as the original condenser.
3) Will a small amount of unknown oil in the valve systems cause issue? Do they need to be cleaned/cleared of oil? Will the AC cleaning solvent cause issue with internals of the valves?
Thank you for assistance.