Ditch the funnel filter. I used it once. Either whirlpool, let it settle and siphon from the sides or just transfer everything and it will eventually settle in the fermenter. Cold crashing can sometimes help as well.
I'd just set it at your desired serving pressure whenever you're able and leave it there. Another option since you're travelling with the keg is to prime the whole keg with priming sugar and let it carb that way. Then just chill and serve.
I just used a hop bag/muslin bag to dry hop an IPA and it worked great. Nothing got in the way of the racking cane when transfering. They do expand quite a bit so make sure you use a large enough bag or multiple bags.
Not entirely sure but here's a real cheap way to accomplish this. You could always try this and if it's not to your liking look into a new faucet.
https://www.homebrewtalk.com/f14/you-can-use-syringe-create-foam-77768/
Also if you're leaving the psi really high for a few days i'd disconnect the beer line. Too high of a pressure can actually push beer out the picnic tap even if its closed and you'll end up with a mess and an empty keg.
Yep, you can lose some volume out of the blowoff tube but I wouldn't worry too much. After all its doing its job and you'll still have plenty of good beer left.
I really enjoy an Altbier I made. I never had one and commercial examples are hard to come by so I made my own. Not sure how it compares to the ones in Germany but it's delicious.