I pulled the vacuum with my Mastercool 5CFM and it goes from 27 to 20 in 10 minutes and up to 5 after around 1 hour... I pulled it for a long time (1 hour) and still it slowly goes down (or up, whatever!)

I am thinking (hoping) that in a positive pressure situation, it might hold well. I'd like to test this, but here in Canada finding refrigerant is a nightmare and somewhat expensive as compared to US.

So to avoid potentially wasting 50$ in refrigerant, I was wondering... hope this does not sound crazy: Can I use my weak little electrical compressor and pump some psi of air into the system to see if it holds it? I do understand that I will be pumping moisture too, but I would re-vacuum anyway. And I would not run the compressor during this time. Any high risk harm in doing this?
I can't think of any, but please give me your advice.

Going to A/C shops up here you get taken advantage of BIG TIME. Most of them refuse to touch your car unless they believe they can make at least 500$ off of you... and will claim they found a leak that might be completely insignificant.

Please let me know what you think.

Thanks!
Greg