1. We just use hooks, as you can get way more towels along a given length of wall if required. We have one bar of hooks on the outside of the bathroom door, and a whole bunch of individual ones that hook over cabinet doors.
2. We don't use it direct, but it is not far from where we hang things. You do have to make certain you exhaust any moist air created.
3. Never used and electric blanket, and don't really like the idea. Besides, I boondock mostly and don't want to spare the power. Instead we use comfy sheets, a woolen blanket, and a fluffy down duvet. Or of course, any combo of those depending upon temps. We set our nighttime temp for the furnace
at 8°C, and would go lower, but condensation becomes an issue. I MUCH prefer snuggling with momma to warm up, than the idea of an electric blanket.
4. Hard to say how long a tank will last, it all depends on usage, including furnace, hot water, and cooking. I would say we get an average of 10 days out of one. We have two, and it seems like we only fill a couple times a year, tops.