1. It depends on your efficiency, but even at 70% you will be pushing 9% abv.
2. Big lagers need ~4 times the yeast that a regular gravity ale does. So either build a starter (1 gallon), pitch onto the yeast cake from a low gravity lager, or buy more smackpacks. Proper yeast health (pitching rate, fermentation temps, pitching temp, aeration, nutrients etc...) is especially important in a beer like this where there is not going to be a lot of malt/hop character.
3. You would save a lot more color by going with a pils instead of a pale. Belgian Pale makes for a surprisingly pretty dark beer on its own. You are up above 30% adjunct by gravity contribution, that is as high as I would push it on a first run.
4. Lager half the beer away from the light and taste the difference, it does not take long for a beer to skunk. Good luck.