Using the kitchen scale is in no way over the top! All the airlines I’ve flown to Europe have weight limits for carry-ons, and some are pretty low (only 8 kg / 17.6 lbs for ITA!).
REI is our go-to for hiking pants, not all of which look like hiking pants. The REI brand is good, also Kuhl, Patagonia, and Marmot. I think they are mostly nylon with some spandex or other stretchy material. For tops, a lot of them are just basic athletic tees (or long sleeved ones too). They’re light and dry fast.
Don’t think of it as packing for a month. You’re packing for 7-10 days, and doing laundry along the way. Going to a laundromat can be a very interesting living-like-a-local experience!