Can't bleed brakes 95 chevy g10

I have a brake problem on a 95 chevy g10. I got used to just unscrewing
the bleeder nipple and being done. The van had a disc brake frozen on the
driver side so I got it pryed off and replaced. I just couldn't get it to bleed.
The brake fluid looked bad so I started looking at the master cylinder and
brake booster since it didn't seem to go to the floor like it should. I replaced
those as well. I still have a brake light and I still can't bleed brakes. I
stomped the brakes out as hard as I could and found a leak on the
modulator. I'm unfamiliar with these and never dealt with one. I read on
here I need to get an OBD II computer to reset it? I'm just not sure that's
the complete issue or what. I took it off and tested the motor. It seemed like
power went through fine. I undid the bleeder screws on the modulator but
nothing new happened. the fluid stops when it gets to the modulator.
Please help me figure this out. I can't seem to find the part for sale either. I
feel like I'm stuck with what I have. I put down astro but it is a g10. It's the
year before the Astro.