Removed the Power Brakes and swapped to Manual Brakes. Got Questions!

Ok so like the title says I swapped over to manual brakes on my 71 Scamp. I have disc fronts, drum rears. I kept the stock proportioning valve.

First off, I swapped to a 15/16" bore master cylinder from a 75 Dart, with manual brakes, which is brand new.

Second, my brake light stays on the dash. No matter how much I bleed them.

Third, the pedal just dont feel right. Say Im driving about 60 and let off the gas and slowly push on the pedal I can feel the brakes slightly engage, but then the pedal goes almost all the way to the floor. It will then hit a super hard spot near the floor and I have to almost stand on the brakes for the car to stop.

What is going on with these brakes?