It's so exciting you're planning on walking along the west coast of Ireland! I'd love to answer all of your questions. :) Will this be your first visit to the Emerald Isle?
1: I've had a look, and was able to find a GPX on the following page. (https://www.activeme.ie/guides/wild-atlantic-way-scenic-drive-west-of-ireland/)
Take a look at the Ireland.com page as well for more helpful itineraries
and information on walking and hiking
2: The official Wild Atlantic Way page
has some detailed and official maps as well, so feel free to reach to them too.
3: A great place for finding detailed walking routes in Ireland is the Irish Trails page
. Under 'categories' you can select 'Walking/Hiking' to search for the right trails.
I hope this was helpful, and please don't hesitate to ask any other questions here!