I'm taking another shot at Asatru, except I'm putting a lot of effort into the Celtic pantheon, I'm going to look into CR more, but until I feel comfortable with it (which I doubt I will) I will stay as an Ásatrúar.
Because I primarily practice a form of Anglo-Saxon Heathenry/Asatru, I tend to include a lot of Celtic elements, specifically Britannian/Welsh and Gaelic, including the Horned God. I also include elements from post-Christian legends and lore, such as King Arthur, Robin Hood, etc.
While there is very little on pre-Christian Anglo-Saxon paganism, I believe there's enough to remake it for the modern Anglo-American world.
It seems the Romans and the Celts had the closest associations among European Pagans. It might be possible to bring elements of Roman beliefs, and perhaps Hellenic into it if you wish. For example Hercules/Herakles/Ogmios.
I would say so. It seems to me that there are very close parallels among the Indo-European pantheons, and most importantly the worship. I know little of Celtic deities but I daresay that an offering of fruit, grains, wine, flame, etc. would be no different for Freyr, Cernnunos, Apollo, or even Thor (he loves all kinds of good food and drink ). It's just the deities one is drawn to who are different, but yet not so different. Heck, I can imagine Thor and Herc pounding down a few flagons and laughing it up after a rough and tumble night kicking monsters' butts.