I have an alternative solutions to what you are looking for. You can enable cloud saving in the general settings in-game on the first computer where you have your characters. Maybe someone else knows what files are involved for a more satisfactory response
Normally you can’t but if you are still in Normal/Vetran or Elite difficulty you can change your mind in the following difficulty. (I assume while playing for the first time you didn’t even notice you were making a choice like the first time I played :D)
you cannot respec the points you invest in mastery bars nor attribute points (i.e Physique, cunning, spirit). Also note that what applies to the blacksmith also applies to your choice between Kymon and Death Vigil factions. What people usually do (or at least I) is to choose one in Normal/Elite buy as much Augments as they can then pick the other faction in Ultimate.
…\Documents\My Games\Grim Dawn
Exact location depends on your operating system.
You can choose another blacksmith in another difficulty (let’s say, one Blacksmith for Normal and another for elite). Then, you’ll be able to use any of them by chosing corresponding difficulty. If you already screwed them, dont bother, cause most useful blacksmith is Legion Blacksmith anyway.
Not many, but there ARE.
First, you cant respec attribute points (physique/cunning/spirit). Second, you cant respec skill points, invested into mastery bar. Keep that in mind, because many builds dont max both mastery bars.
Did you purchase thru the website or thru Kickstarter?
Anyway it goes thru Humble
If you don’t have an account at Humble you would use the Key Resender https://www.humblebundle.com/resender
Input the email you used with your purchase.