As to bows:
I'm not sure how any Dwarven bow would be a "long" bow
However, I can see the possibility that Dwarves could still be very effective archers,
assuming that they accepted the years of training and practice required.
With a simple or "self" bow, both its power and its draw-weight are direct functions of its length. The classic English longbow, which was fitted to the archer by matching the length of his outstretched arms, managed (probably as a result of trial and error) to come up with the most efficient possible configuration for a simple bow, one where at full draw the bowstring makes essentially a right angle. This maximises the power available for a given draw-weight, which in English examples was as heavy as a trained man could manage.
It's certainly possible to get equal power from a shorter bow using composite construction- but the tradeoff is that, since the bow is shorter and therefore provides less leverage at the tips, the draw weight for a given power is considerably heavier; or, looking at it from a different point of view, since a short composite bow on the Asian pattern can still have a draw no heavier than a man can handle its effective power is less. In other words, a shorter bow is simply less efficient, no matter how clever its construction.
Having said all that, though, these are Dwarves- which means they might well be able to handle a draw far heavier than the 180-200 lb-f a strong man can master, and thus potentially equal a longbow's power in a dwarf-sized weapon.
Still, it seems to me that the Dwarven love of devices would have attracted them rather to the crossbow- which also doesn't require the training and practice (archery ranges underground????). Moreover, one would expect Dwarves to be able to handle hook-and-stirrup cocking of much heavier crossbows than human examples, and thus avoid the rate-of-fire penalty of the various crank systems.