Worse news - I do not think your car used the same valve that my car (a '73 220D) used - bad news because I have an extra valve which I would part with but it will not fit.
Looking at your photo and mine you will notice that on mine the two cables seem further apart and they are level with each other, also the platform the valve sits on is right under the two cables on mine and the rubber lining of the fire wall has a single hole for all of them.
I suspect you had this valve - number 25 in this image
the image is small but it seems to fit you car - it is taller and the controls are closer together. Notice two hoses connect to the front and one on the side. We need to find someone with the right valve that we can photograph and maybe get a part number off of - then check salvage yards (many are on line and are easy to use).
Two other things I notice in your photo:
1 the ends of the cables still have their round ends - that's good, you might not have to replace those cables, the round ends snap on to the control handle.
2 the second cable that goes the the throttle - This is so wrong that it might take another thread to straighten it out. It is easy to fix with a new cable and it will make your car easier to drive when cold.
The cable that goes to the throttle is from the thumb screw that lives on your dashboard between the key and the "salt shaker" glow plug indicator. The thumb part may have broken off (these are easy to replace and perhaps the cheapest thing you will ever replace on this car). You would use this on a cold morning when you turned it the cable would tighten and open the throttle a bit more. This would make the engine run faster until it warmed a little bit when you would turn it down.
To replace that cable you unscrew it from the dash, disconnect it from the throttle and remove it and run a new one through a hole in your firewall just above your accelerator. then connect it to your throttle.
The rest of your heating system depends on finding the correct valve. Very unfortunate that you don't have the original since it probably only needed new O rings.
To recap: you asked about the correct fuse ($10 max if you replaced all of them). You got back:
1 replace the heater valve (God knows $$ - if you can find one)
2 replace the hoses so they fit better ($10 - $60 depending on what you need
3 replace the idle control cable ($60 one example
4 possibly the thumb screw ($0.59 - at least something is cheap
It's a wonder more folks don't ask for help