I will try to answer your questions in the order you asked them.
1. I like to leave the pump on for at least an hour if possible. It will help get out any mosture which may have gotten in the system.
2. Vacuum loss is very hard to determine as the ambiant temp will have an effect on the readings. If it held vacuum for 18 hours, you are good to go.
3. You can use the low, high, or both. It doesn't matter.
4. I would go ahead and recharge the system and run it a little every week or so. If you don't, some of the seals may dry out and leak when you do recharge.
5. There is no way to say what the pressures will be when you recharge as the ambiant temp makes a BIG difference. I would charge by weight and not worry about pressures at this time. I'm not sure what your car holds but if it calls for lets say 36 ozs then put in 3 12oz cans and don't worry about it.
As far as the amount of oil to add, always go with the max, not the min. If it turns out to be 2 ozs low, you may be puting in another compressor. If you go 2 oz over, you will never know it. Just don't put in an excessive amount as cooling will be affected.
If hope this helps.
84 500 SEL (307,xxx miles)