I see no improvement in the pedal feel at all or braking power. I did notice the front pads seemed to only be making contact with the outer half of the rotors (as the inner half keeps some light rust.

Sounds like you have northern rusted rotors - that's why the pads are not touching all of the rotor surface. If so either resurface (bad) or replace (good) the rotors and pads first - to get the pads to touch all of the area they are supposed to.

And yes it's a very good thing to flush the hydraulic system every 2 years or so.

 

I'm dealing with the same issue. Replaced brake booster, rear rotors and pads, nothing changed. No idea what's wrong.

 

Did you just replace the vacuum booster or including the master cylinder?

 

Usually when Master Cylinder goes bad the brakes work but leak off when holding with brakes at a stoplight or stop sign. Sometimes the master cylinder will leak into booster and ruin it also and sometimes the master cylinder has a leak that can’t be observed. I see no mention of the Calipers they can freeze up with internal corrosion due to old brake fluid.

 

Pistons were moving fine when I changed the front pads. No cracks on the rubber. I bled out and replaced all the fluid in all 4. Rotors are equally hot when taking the car on a drive around, just apparently not touching the pads fully on both sides as there remains surface rust on the inner half of the surface. Car is not pulling on either side, so I figure the calipers work, although maybe not to full pressure...

On a standstill, the pedal slowly sinks in, however the car never starts to creep forward.

 

Just in case I share my last experience with mushy brakes after rebuilding my frontend.

I also bleed the brakes few times. Reseated everything few times. And every time brake pedal travel was too long before started real braking. I also have partially rusted/not fully / evenly in contact front rotors and pads. Was already googling about ABS pump or master cyl replacement costs. Finally, I was so pissed and just popped the anti-rattle caliper clips/springs off trough wheel spokes (found someone to suggest it, very random I know) and instantly brakes worked as normal.

They were not installed wrong way (double checked), but still somehow they were related to the problem. Somehow they lifted pads just enough off the disk that I needed to press pedal very far before actual braking started.

 

Just in case I share my last experience with mushy brakes after rebuilding my frontend.

I also bleed the brakes few times. Reseated everything few times. And every time brake pedal travel was too long before started real braking. I also have partially rusted/not fully / evenly in contact front rotors and pads. Was already googling about ABS pump or master cyl replacement costs. Finally, I was so pissed and just popped the anti-rattle caliper clips off trough wheel spokes (found someone to suggest it, very random I know) and instantly brakes worked as normal.

They were not installed wrong way (double checked), but still somehow they were related to the problem. Somehow they lifted pads just enough off the disk that I needed to press pedal very far before actual braking started.

Oh wow. That is absolutely it. I double checked those springs, and sure enough I had them with the "ears" on the wrong side! Reseated them properly and instantly improved the brake feel and efficacy! You good thing to check and very easy to mess when doing a diy brake job!

 

Just be careful, I had one of those springs pop itself off and I was getting a bad rattle from that corner. Realized I was missing the spring, put a new one back on making sure it was secure and all was well. I've never had issues with the springs when installed correctly. Always check and service the sliding pins when refreshing the brakes, and replace sticky or rusted calipers ASAP.