Diablo – Transfer D3-UEE Xbox 360 to D3-UEE Xbox One

You might still consider mice, as there are Trackball mice which are similar to normal mouse precision but operate in a different way:

This for example is the "Logitech M570 Trackball". Basically instead of moving the mouse on your table you move the Trackball with your thumb. Your shoulder does not move a bit.

There was once a top professional Counter Strike player that used a similar mouse, but I forgot his name, which proves that you can make it work even in precision games that require fast reflexes. Here is an old discussion about this topic: Gamespot Thread

This does not really concern your question, but I guess you are using your mouse in a wrong way. Day[9], a professional Starcraft veteran has a 1 hour show that explains how to correctly use your mouse and keyboard for Starcraft 2. You can easily adapt this to Diablo 3 or any computer game. Check it out: Day9 Daily 252.

Once you have unlocked a difficulty level, you can play any act/quest on that difficulty level if you join a friend's party. (i.e. With a brand new character, you can join someone on Normal Act IV with no problem, but you can't join someone playing playing Inferno act I).

As for mechanics, if you haven't unlocked an artisan (such as the blacksmith), joining a quest after that artisan is unlocked will instantly unlock them for you.

The problem you run into with jumping straight to later quests is the exp penalty when playing with characters who have a major difference in level. You are expected to be playing with other characters within 5 levels of your own, and if you aren't there are experience penalties for the lower level character if the characters are more than 5 levels apart.