Yes, but a .223 suppressor will be overkill (large and heavy) on the .22.
Yes. For trusts, guntrustlawyer.com Also, there are some historic books on suppressor designs but most of the info is dated.
POI change depends on several factors and is not entirely just the suppressor or the host firearm.
.22LR suppressors do accumulate gunk.
If properly made, no.
I have a bunch of tech notes about some of these topics over on the TBAC web site