Numbchux

Pads in backwards? What kind of pads and rotors did you use?

I'm sure it's been done hundreds of times. There are universal usb ports all over the internet. I bought some simple ones on ebay 10 years ago and installed them in my Celica. I tapped into the power for the cigarette lighter, and cut new holes in the stereo surround to mount them.

Any 5-speed manual from 2000 or newer will have the housing you need. A WRX has different transfer gears, so it might be best to avoid those in case you need those. Here's the parts diagram of the rear cover. You definitely broke the cover, callout number 32130, might have damaged the bearings or shafts inside there. Disconnect the shift linkage, remove 9(?) bolts, remove housing. Transfer bearings and shafts from old to new, apply sealant, reinstall bolts, reinstall shift linkage. Could have replaced just the ujoint probably 6 months ago. But it likely chewed threw the end caps and into the yoke since then, not to mention the damage done when it broke. This one just had a vibration. This one is too far gone for a good repair 20180105_185438 by Numbchux, on Flickr Here's a yoke after a joint failure.... 20190602_191605 by Numbchux, on Flickr It maybe could be botched together. But for the $50-100 for a used shaft, I wouldn't mess with it. www.car-part.com is a great resource for used parts. Frequently they will list transmission cores on there, which might be a cheap way to get your housing.

Looks like a manual. So no, can't drive it without the shaft. Completely fixable. extension housing can be replaced in the car. Buy a donor transmission (can even be blown up) for $100 or less and a "new" driveshaft, spend a few hours crawling around in gear oil, and it'll be fixed. I definitely would, but I just put a brand-new rear subframe in a rusty '00 Outback with 325k miles on it, so I might not be the best person to ask.

Vibration under load is textbook Ujoint, I see no reason to question that diagnosis. Driveshaft ujoints can fail, and they can fail catastrophically. Replacement joints are about $30, and a decent pain to install. But if it's left too long, and chews through the cap and into the yoke, you're looking at a new yoke, and shaft balancing, or replacing the whole shaft. The vibrations are transmitted right into the differential/transmission, which is not good for the bearings inside them. If it breaks entirely, it can destroy exhaust components, shift linkages, and I've even seen them break off a chunk from the rear of the transmission. Here's my saga on diagnosing and replacing them myself: https://www.subaruoutback.org/threads/driveshaft-u-joint-replacement.465866/

Don't hold your breath....it's been a nasty one.

My money is on front ujoint in the driveshaft. Slipping clutch feeling is the center VLSD trying to send power to the front. Gear oil will leak out if the slip yoke has fallen out of the transmission (or if the damage is bad enough, it can damage the rear transmission housing). It can damage the shift linkage.

Don't need a different master, just an M10 union.

Yep, if that's the only code, you likely need the sensor. 2-wire sensor, aftermarket listings usually have the one for the gauge listed as a "switch" and for the ECU as a "sensor", but that can vary.

Completely normal. You can waste electricity to warm just the transmission (when everything else will still be cold), you can waste gas to idle the car for a few minutes to warm everything up before you drive, or you can keep it below about 50 to let things warm up while moving (your gas mileage takes a hit much above that anyway).

Anything 2005 or newer (since you didn't bother to tell us what car you drive....) will disable the cruise control with any check engine code. This is not a cruise control fault.

Yep, flange is welded on. An exhaust shop could probably fix it quick and cheap.

No bleeding required, this can be done in about 3 minutes with just a pliers. It's in the rubber vacuum hose between the engine and brake booster (if you need more info, google some of those terms and all your questions are answered, this stuff is used on all gas engines with vacuum boosters). Those sound like the right plugs. Are they fairly new?

Brake problem is a frozen check valve in the booster line. I've had it happen on most of my cars, and have had good luck cleaning it. Pull it off from the booster, and squirt some MAF or Carb cleaner in there, let it sit for a minute and then start the engine, and spray some more through there with the engine running. "Correct" fix is to replace that booster hose. As for your misfire. I'd throw a set of NGK Copper plugs at it, their cheap and easy for that engine...

Phase 2 ECU will not easily control a Phase 1 engine. I've heard of people diy adapter plates to put the Phase 2 intake manifold on a Phase 1 engine, then you have all the matching sensors. But it's not a great option.