With regard to the decimal switches you first tried in the video.
I've bought quite a lot of these, the contact resistance on them can be bad on some digits if you don't clean them up first - probably they have been stored in some China warehouse for 10 years. So really important to check each contact on all the switches before you do assemble, any dirty ones, squirt some switch cleaner lubricant on the back of the board, let it soak through the wiper center then work it through.
If it's really bad, shave off the lugs on the back, pop off the board and clean up the contacts manually. If like me you have to check and clean up about 60 of these critters at a time, you do wind up with a sore thumb for a while :-/ I considered using SMD resistors too, but the power limitation put me off, standard 1/4w through hole resistors fit fine if you bend a leg on them.
To null out the combined contact resistance across the decades, I just reduced the 1st 1 Ohm resistor to 0.5 Ohm, so as long as the last number in the series isn't 0, the contact resistance (which totalled 0.5 Ohm for me) was essentially taken care of.