No, he doesnt need to touch anything, any more than he touches the wine (which he doesnt, its in a chalice)…
Amputations and such certainly have been impediments in the past and even now. But this is not because of any invalidity issue…its because they couldnt preform the rite as the Church specified. Theyd be able to do it validly, but not licitly (because the rubrics do require elevation of the chalice, etc)
Yes, he needs to be morally present to consecrate (or absolve, etc). It cannot be done by phone, radio, etc (although blessings can be because they are simply a prayer, a canonical declaration setting something apart for sacred use, not a sacrament)
“Morally present” is rather vague, it means generally considered truly present. Usually this is defined as within a range of unassisted sensory perception to the matter of the sacrament (he doesn’t have to actually see the matter, it could be inside a box or ciborium, it just has to be within the range where he COULD reasonable percieve it if no obstacles were in the way). A priest could probably absolve someone, as long as he could hear the confession by unassisted screaming, across a field (or across an expanse of water, etc) Ive heard Aquinas says the distance for eucharistic consecration is about 20 ft (I dunno how he got this)…I dunno if, based on the sensory perception definition, a REALLY big host could be consecrated from farther away or not…the priest has to just generally be considered to be in its presence…its a “you’ll know it when you see it” sort of thing.
As for signing the words, or writing them out, or drumming them in morse code…I dont think so. I think he has to verbally speak a true human language that really conveys meaning (“word” and “voice” being important symbols in Christianity) As for languages that no one speaks, like “elvish” or “klingon” or in some sort of code…Im not sure, probably not…it probably has to be a real spoken language. As for something like Esperanto, spoken by some (even a handful as the native language they were raised in as a baby) but which was constructed artificially…Im not sure, maybe.