Charge/Evac Equipment Recommendations

Maretu

Hey all. I'm looking to upgrade my A/C equipment enough to take the guesswork out of charging and evacuation and was looking for a few recommendations.

I keep reading the little cans are extremely unreliable with weighing an actual charge into a car, and I feel this is where I'm messing up sometimes. I'm able to source a 30lb R-134a cylinder locally for about $130 which seems pretty cheap to me, considering 30lbs in the little cans cost 190 ish. I had my A/C flawless last year before a shaft seal blew and now I can't get the damn thing back as good as it was. It was pulling 52-55f at idle within 30 seconds on a 95f day and now I can barely muster that on the highway after replacing a compressor with no other changes. -_-

I was also wanting to add a micron gauge https://mechanicguides.com/best-micron-gauges/ and a refrigerant scale to my arsenal because I've been charging with a regular manifold gauge and cans. Do ya'll have any recommendations on good brands and where to get them? And whether a postal scale might suffice for DIY home charging?

Also, how much would old vacuum pump oil or a re-used receiver drier affect the final micron reading or performance? I currently have a 7 year old 2-stage Harbor Freight vacuum pump. This is another reason I'm interested in the gauge because a proper vacuum is only a shot in the dark for me right now and this may be where I went wrong.

I really appreciate any replies!