Who will allow me to use cannabis but still hire me?!

I have had my card for many years.
Whether you have a prescription or not is irrelevant.
Since it is still in a legal grey area, I know of no employer that would hire you or anyone who is a cannabis user. Although I am sure that there are some out there.
You doctors recommendation does not protect you.
Cannabis users are not in a protected class.
Unfortunately. In the future this will change.

The first thing you need to do is get a letter from your doctor showing that you need cannabis for pain relief
If your position doing something that could impede your fast judgment then you should not be working there, like operating machinery, driving a company vehicle to name two.
You should also explain this problem during the interview and show them the letter. A lot of people don't know that companies are also guided by their insurance company re guarding what the company will cover due to an accident.

most construction employers,their attitude is if you make them money you have a job, just that simple

If you have a medical card for it, then no one can refuse you based on the fact that you use it. They will however, not permit you to use it at the place of employment, and not allow you to be under the influence while working. If you don't have a medical card than nobody will hire you if they know that you smoke cannabis. So you have to options: get a card, or fake the drug test and do not inform your employer. If you choose to get a card, you may have to move to a state that has legalized cannabis for medical issues, or if you choose to fake it, go to google and type in drug test passing kits.

Common Sense? and many years of research on the subject of marijuana

Did you really just compare weed to alcohol? Let's take a look at this ok? Weed is illegal and the fact that it is the "only medication" to relieve you of pain I find very difficult to believe. Even if that were the case the only way they WOULD hire you is if it was medicinal which I still don't believe is right. Alcohol isn't harmful only when abused, just like everything else out there. When your sick you take medicine, you abuse it and you become sick, same with alcohol. You drink too much and then you get sick. It takes self-control. Stop the drugs if you want a job.