1: No, wearing glasses does not affect your vision in astral projection. ( or at least I don't have any problem since I too wear glasses )
2: As far as I know, this depends on how strongly you project yourself, Or, how sensitive the animals are.
3: There are many ways to re-enter the body, most just simply wish themselves back or pull themselves out of the trance like state.
Check out this, https://www.spellsofmagic.com/coven_ritual.html?ritual=1518&coven=245, and just kind of research it in general for more if you don't understand much of it.
1.) Astral projection is perception with a different aspect of yourself than your physical eyes. If you choose to 'wear glasses' on your astral self, that is up to you. But you should be just fine.
2.) This is where more debate might happen, and some might consider it a matter of semantics. There are those who insist that Astral travel is on the spiritual plane, whereas out-of-body travel on the physical plane is ethereal travel. Some may suggest that this is where they believe ghosts -- spirits of the dead who have not moved on -- reside.
It is a matter of belief, really. Some may think that some animals can perceive them, while others will not think so.
3.)You never actually separate when you do astral travel. It is more like extending your awareness to the realm, than like actually going somewhere else. If something disturbs you physically, such as being touched, or there being a loud noise, you just come-to. If something disturbing happens while projecting, you can simply return.
There is no time or physical distance on the non-physical level. Travel may be perceived as distance, and distance may seem to be experienced, but it does not require actual movement. Rather, it uses will and intent.