Tell them that you stutter right off the bat so they are fully aware but turn it into something positive,for example,that your a better listener,more inclined for teamwork,a people person,that your humble and down to earth. While reading your post,it was a bit creepy because it sounds almost like me,im 34 with a very spotty work history myself<also got a job interview coming up soon that im extremely nervous about>,most of my jobs have been stocking for supermarkets and temp jobs in production lines. I reccamend listening to stuttering podcasts as well,theres a few out there,also tons of vids of ppl that talk about stuttering/blocks on youtube as well.I know exactly how you feel because i have a severe stutter myself and it gets unbearable at times and im stuggling too.