will you ever be able to buy 20sps for 10pp again?
Yes, if you lose a lot of veterancy SP will become cheaper again. I.e if you have a hundred games played but no vet or SP in the pool your SP will be very cheap. It only gets expensive as you have SP sitting in your company (either in the pool or invested in unit training)
The luftwaffe air recon is intended to circle the battlefield for a short period of time. Somewhat like a Henschel.
It's also supposed to be 1 free use. Does it actually say 'completed'?