Can I only do pve in elder scrolls online if I want to?

Yes. The pvp is confined to one zone which is cyrodiil. So if you never go there then you never have any sort of pvp.

Yes!

90% of it is pve so why not..

Yes with two exceptions

You can't use the keep guild stores without going into PvP so buying things will be a little harder.
There is PvE content and quests inside PvP that you won't be able to play.

It's very easy to avoid PvP if you're just visiting guild stores in Cyrodiil, and you can still do the PvE content. There's just a varying degree of risk of being killed by an enemy player depending on the location of said content.

Yes, you can just stick to PvE throughout your time in Tamriel, however, if you ever want to try open PvP, even after you ding 50 and get geared to the teeth, you can do that, too. So it will always be there for you too, just in case you ever change your mind.

There is no PvP in ESO, only AvA.

Yes. You can't accidentally stumble into the pvp zone, so it will always be your choice.

Technically true since there isn't even dueling.

Once you hit 50 you are automatically converted to be Veteran Rank 1.

When that happens, Cyrodiil mobs do not drop Veteran rank gear, they give zero Veteran experience, and the quests in Cyrodiil give extremely poor Veteran experience for the time it takes to complete them.

As a result, unless you want to become involved in the alliance versus alliance war, you will have very little reason to ever have anything to do with Cyrodiil. You might want to collect some skyshards or perhaps visit a guild store of a guild to which you do not belong, but that's pretty much it.

Honestly not a jab Davidm, but you should really gather up all your questions and make a single post asking them all at once. Then you could bookmark the thread as your own lttle mini-TESO wiki.