No brakes at all to be able to drive?

The brakes went out on my car so I was replacing them and I noticed the brake line to the driver back wheel had been cut so I bought the stuff and repaired the line with flaring tool, line, etc. I put brake pads on all wheels and tried to bleed them and no e would bleed because bleeder valves were stuck. I bought 2 new calipers and put on front(yes they are on right, valve at top)and they bled fine. But there was no brakes at all to be able to drive it. The master cylinder had no cap so I bought one, took master cylinder off and emptied out fluid, cleaned, put new fluid in it. Still no brakes. It has also developed a vac leak under the hood I can't find and after it runs a few mins u start to hear the hissing sound and the car acts as if it's gonna die then comes back up then dies down then back up over and over at idle. The back passenger side caliper would bleed if u turned the banjo nut, I got the valve unstuck, now no fluid to it and no fluid to back drivers side where I replaced the broken line. The brakes worked before but they needed changed because it would hardly stop and had started screeching. By changing brake pads this is what my results have been. Multiple people have looked at it and no one knows what to do. Idk if it's the master cylinder, or what. The brake pedal is very easy to push there is no pressure at all and goes straight to the floor. Changing brake pads has lead to my car being set up for close to a year now because it can't be driven at all because it has literally no brake at all. And I can't figure out why the 2 new calipers on the front aren't giving it at least brakes In the front. What can I do?