And, of course, bats as large as flying foxes fly just fine with short sterna, small sternal keels, and humeral elevations around 25 degrees.
Do you just mean the elevation of the humerus above the glenoid, or the elevation of the wing above the body? That's the same in birds, but not in bats. In bats, the joint between wing and body is the joint between clavicle and sternum. Using this trick, I can "lift" my arms something like 40° dorsal to my body. My scapulae are positioned dorsally, and so are those of bats. I have trouble imagining that bats have more restricted upper-arm movements than I do.
2) No extant glider with a mass within an order of magnitude of 180 grams functions without a drag - providing tail
Is that what the tail does in gliders? In flying birds, the tail -- which is, of course, very different from that of any glider -- reduces induced drag (I can probably dig up the paper if someone is interested).