I'm a little confused if you have cable clutch or hydraulic. The brake pedal getting tight. Unless the cable puts side pressure on the spacers it loses me.

I'm thinking if your pedals are sticking. The rod that runs though a bracket that holds them both up under the dash, may need lubed.

Next, if its just the clutch it could be as some one posted about the lever.

I had a clutch do what you described. It turn out that a spring fell out of the friction disc. There four of them, in pockets. They reduce shock to the transmission input shaft splines.

It happened all of a sudden without warning.

It jammed itself between disc and the pressure plate finger springs. Rare, I think but it happened.

If I would have kept trying to push it I think it would have damage the cable.

A hydraulic cylinder unit could blow out a lever and who knows what. Then you would have a loose pushing clutch pedal. Extended slave cylinder with no return pressure.

Either way the clutch does not release.

Let us know what you find down there!

I think McDuck is correct. The clutch arm often wears out at the fulcrum point. See the attached picture.

I don't know the details on the clutch on the 740 (I should since I own one), but IF it's a hydraulic clutch, it would have a slave cylinder, and IF the fluid is shared with the brakes (some hydraulic clutches are set up that way) and the slave cylinder had an issue it could conceivably cause the issue you experienced. A non-releasing clutch can indicate a failed slave cylinder (again, only if your car has one) unless as already suggested there's a mechanical failure. If it's a cable-operated clutch, maybe pumping the clutch pedal against whatever blockage was there caused the cable to snap.

Zack
1980 245DL M46 291k
1988 745T+ M46 234k

Don't know about the brakes, but it sounds like you've broken the clutch release fork. You'll have to get under the car and look.