Bugger, bugger, bugger!!!
1.020 is definitely a bit too high. Mine finished at 1.010-11, but should've finished ~1.013. So i assume it's definitely tasting a bit too sweet? If you could get it down to, say, 1.015 that should be fine.
How long has it sat at 1.020?
Have you tried rousing the yeast with a bit of stirring, etc?
If not, i'd try that. Sterilize your spoon carefully, of course, but it should be easy and safe. Hopefully that might wake it up and knock off a few more points. (Also, just giving it an extra week if it's only ~2 weeks in).
The next step is a bit/lot trickier, if the rousing fails.
Re-pitching yeast is a bit more complicated than normal, as this beer not just has some alcohol in it to start with (that'll shock the yeast), but a LOT of alcohol in it.
You could try just tipping in a packet of something, like Belle Saison or Notto, but there's a good chance it'll either die or just take a really long time to ferment it out (as there's only initially a small amount of yeast in a little packet).
Ideally you need to quickly whip up a starter of whatever yeast you choose (so you could also use a liquid for this if you wanted - basically pick something that will handle high alcohol content). This is to both build up numbers, but get the yeast used to an environment with alcohol in it.
Ideally you might do 2 starters, one to get it going and build up some numbers, the second to build up the alcohol a bit further. But that's probably too much faffing around (& time lost!).
I'm thinking you might be able to do you starter, then add some more DME+water (boiled & cooled) to that starter once it's gotten through the first lot of sugarz to crank up the booze level and condition the yeast that way. Obviously the 2nd addition would need to be concentrated otherwise you simply increase the volume without increasing the alc%.
If that all sounds too much, simply do a single starter and toss it in and hope for the best.
Obviously once the starter is fermented out, you'd chill and decant off most of the liquid, then stir and toss in the yeasty fraction.
How's all that sound?
This is at shed temp around 12-14c and the malt is just diabolical, probably should have chilled a little, but **** it's a great beer. Well done techno!!
