Bard has a lot of buttons to push - Infact i'd argue that out of all of the ranged DPS classes it has the most. With this in mind, why bard? I have to play devils advocate here but if you run any lvl 80 content with your disability, on a job with a lot of buttons, you'll find yourself unable to clear some content and perhaps even be the target of some harassment by those who do not know about your situation.
Might i suggest something a bit simpler? Perhaps dancer, machinist (though its a little fast paced) or a healer like white mage that in dungeons you only really need to press a few buttons to do the basics of your job? With healers you can even have mouseover macros too, which means you only need to hover your mouse over a part members name on the party list, reducing the clicking you need to do.
Do you play on controller or keyboard/mouse? Have you tried alternative control methods? Perhaps some pedals for your feet bound to a keyboard button press? Lots of different sizes and shapes of mice out there too for all different purposes, hell i think with enough effort you could probably play FF14 at a basic level on a flight stick.