Nice. Consider adding 20-50% wheat.
If you're feeling lazy (or adventurous), you don't need to boil.
No starters.
Lacto will definitely sour the beer without a head start.
L. plantarum is the king of quick souring; YMMV with other species.
If you don't want to buy a Lacto culture/probiotic/yogurt, I would use grain. It's less predictable but it should work just fine with minimal risk in this process.
Wasn't planning to boil it. Is the wheat to supply ferulic acid for phenolic compounds? I didn't think kveik yeast (I'm using Voss) was POF+. Or is wheat for head retention or something?
4.5 lbs of base malt and 20 oz of flour should get me just over 1.050 in 3 gallons, depending on the conversion efficiency. I have Belgian pilsner malt, Rahr 2-row, and Rahr pale ale malt; will probably use the pils because it's the oldest. I also have a little cara-wheat and cara-rye malt, but those would probably be out of place.
It will be a cheap and quick experiment, and if it stinks I can get rid of it before Wife gets home.