As for height: you might want a bit less height on your seatpost, and hacksawing it would work out fine. You could probably do at least the first stages of learning inside, because doorframes and walls are wonderful supports, and until you learn to ride farther than a few feet you won’t really need to go outside. I learned in my basement, and there isn’t too much space there.
A really great resource for new unicyclists is the journal of a new unicyclist