A brew that did not go as planned - trying to salvage / experiment / learn

I was trying to thin out my stock of malt as I felt it was growing a little too big and out of control, and besides I have limited space for storage. I wanted to brew a real dark ale again since last time was a while ago, and also Winter was Coming. I was quite happy with my last Bourbon Stout - at least after some extensive bottle conditioning, so decided to make a similar brew, only to substitute the oak chips with a vanilla pod for variation. Thus I formulated my recipe as such: https://share.brewfather.app/Ni1GXfVsvXsuMu

Screenshot of Brewfather recipe for quick reference:

David Heath has been using Lallemand Voss Kveik for a number of Dark Ales, and I tested this too - with good results. I had a packet lying in the freezer and decided it would be fun to ferment with this yeast again.

I ferment in a Bucket Buddy since this includes a heating element that can hold the heat fairly well, and it has the added option of filling bottles directly from the fermenter if necessary.

I also used my Rapt Pill which is currently the most reliable and accurate electronic Hydrometer I have in my posession, which I am very pleased with.

Fermentation and stop
The fermentation started off very quickly as expected, and behaved correctly until it reached and SG of 1.027 and just stopped dead in the tracks. A temperature increase did not do anything to get it starting again. I got some tips from the Norbrygg forum that more yeast nutrients might be wise for Kveik yeasts, so after getting a new pouch of WLN-1000 from Brewshop, I boiled water and added 4 grams of this and pitched. For some reason, the SG reading rose by 2 points which was not expected from my side, but I haven't studied the ingredients in the WLN-1000 that much.

Still no activity led me to the next action which was to try to add sugar and stir the fermenter in order to kick the yeast back to action again.

Fumbling a little bit with the calculations and finally discovering that I could use the Brewfather tools to estimate the amount of table sugar I would use. I wanted to raise this by 1 point of ABV and therefore 10 gravity points. First I missed a decimal and boiled + added 36 grams sugar (which I found very strange), but discovered that the correct amount was closer to 336 (of course), so added additional 300 grams of table sugar boiled in water. I updated the brew recipe to account for the added sugar. I had now also effectively added a total of one additional liter of water to the fermentation tank.

Starting with new yeast
There didn't seem to be any sign of activity which was surprising to me, so I decided to pitch new yeast (a non-Kveik one) and ended up with Lallemand Nottingham after considering Verdant IPA (which I guess are closely related anyway). I let the temperature drop to near 20 C and pitched the packed and stirred the fermentation tank. It started as expected and slowly but steadily started eating away the added sugars. I would have expected it to work a bit faster since the sugars should be easily fermentable, but it might be that the already high alcohol content would limit the reproduction speed.

Brewfather is an awesome brewing software which has an insane value-for-money subscription price in my opinion. For some reason - not all malts include data about their diastic / enzymatic power. I started to suspect that there might be something there that would have impact on the fermentability of my wort. A quick internet search excercise did not actually include much concrete info on what would happen if you had too low diastic power. So I was unsure if I would have noticed at extraction or if it affects the fermentability.

Diastic Power and effect on fermentability?
I looked up the remaining data for the base malts and got a number of 45 degrees Lintner which is beyond the recommended miminum of 60. So if the fermentation with the added Nottigham yeast yields the same FG I would personally be inclined to conclude that if you have low diastic power, it will decrease your fermentability. My mash efficency was almost spot on and around 80% as predicted.