Willamette is Fuggles DNA, but is a Tripliod hybrid, so it is more robust than Fuggles. US Willamette is also different from UK Fuggles, as the terroir will give different flavor and aroma. If you don’t mind Fuggles, plant one of each and see what you think. You can remove them if not to your liking.
Belma is one I would probably avoid as a single hop. It’s not that it has a bad flavor but the flavors are very gentle and it is seemingly impossible to get those flavors to really pop on their own.
Yes, according to the growers the total oils are only .8 mL/100g. By comparison Citra has 2.2 - 2.8 mL / 100g.