I'd be extremely surprised if such tables or database existed, mainly because the number of possible reduced decompositions for a Weyl group element tenda to grow very large as the rank increases. Even for the well-studied symmetric groups, this poses a serious problem. (It also makes tables of Kazhdan-Lusztig polynomials tricky to assemble; in Mark Goresky's old tables, he finds it convenient to work with a particular choice of reduced expression even though this makes it very complicated to compare other choices.)
In your case the Weyl group elements are more specialized but also tend to have huge numbers of reduced expressions as the rank grows. Ditto for the elements of $W$ which support Bessel functions.
A smaller comment: It's legal to invent your own notation, but it's much easier to follow Bourbaki (or another source if necessary). The Bourbaki notation is $w_0$ for the longest element of $W$ and $w_\theta$ for the longest element of the parabolic subgroup $W_\theta$ relative to the simple roots fixed. (Also, a couple of your sentences need to be rewritten, though one can guess what you meant to say by "reduced decompositions of long elements of root systems".)