Welcome! You came to the right place.
This is not essential, but can help depending on the primers you used. Some primers leave very little of the flanking rRNA gene regions in the amplicon — others do, and this can impact taxonomy classification results. I have done ITS analysis without ITSx in the past without issues. (the big issue that can occur, though, is when your reads are longer than the amplicon, as described in this forum post, which is very relevant to your questions).
Incidentally, I just discovered (via this post) a new 3rd party qiime2 plugin, q2-itsxpress, that will perform ITS trimming for you! So no need to export, trim, then re-import.
Check out q2-itsxpress... it looks like this happens after demultiplexing but before denoising. @Adam_Rivers may be able to tell us more!
ITS alignments are not phylogenetically informative except possibly between very closely related species — so don't do the alignment. If you are just doing the alignment for diversity estimates (e.g., with UniFrac), just use non-phylogenetic methods. You could also check out q2-ghost-tree (and @Jennifer_Fouquier can give more details — I'm not sure whether that plugin is still in development mode)
Don't apologize, that's what we're here for. Thank you for posing very clear questions. 
I hope that helps! 