I've spent close to 20 hours trying to bleed the clutch system on my 190d

and it still won't bleed out properly.. the car has been down for close to 3 months now in the process..
I've tried the following:
Reverse-bled with hand-bulb (got it to 50%)
Reverse-bled with hand oil pump canister (got it to 70%)
Reverse-bled with right front brake caliper (got it to 80% once)
I can't bench-bleed the clutch master cylinder as the nut is stripped that runs to the hard-line. And it literally destroys my back to try to even try to remove the master.. (slipped disc in back)
I don't have access to a power-bleeder, nor do I have the extra funds to buy one. I have tried literally just about everything..
What I fail to understand is I put a slave cylinder in this car 9 months ago, and it bled out within 5 minutes.. that was a cheap-o slave cylinder. This go-around I decided to try a Mahle/OEM-equivalent to see if it would last longer and this is what I get..
Really frustrating, this is probably the most ridiculous automotive job I have ever done.
Any tips/pointers?