But we are probably more “weird old wannabes copping some made up blues character lifestyle” than we are blues musicians.
From everything you said prior to this, I don't think so. If you get the intention of the way you approach the notes, and you can improvise with others to build dynamics with that intention, you are not a wannabe. You might be a person who wants to learn more, and it really doesn't matter what you know, because you clearly get what the wannabes don't get.
The problem is that people who don't know what they don't know are going to be standing in deep water very quickly, and that can land them in trouble. There's a little bit of snobbery in blues circles, which is unfortunate I suppose, but if you go to a jam and you don't know any of the historic and rootsy sort of stuff, it tells everyone a little something about you.I don't view it as gatekeeping to comment that the Blues Brothers are probably not the best option for learning about blues music. They're not, for reasons described. I enjoyed their movie, but beyond that ... eh, they were sort of ok, great band, campy blues singers. I guess we have different feelings about their music, I wouldn't call it great myself. Their popularity did bring more attention to the genre, as I noted, so that's a positive aspect.
Now, that's not bad by itself. The jam I go to is quite forgiving and open to players of all stripes, and people there want to share their enthusiasm for the form, so there is a lot you can learn from them, but if you keep showing up to play the same blues-rock stuff over and over again it will begin to get tedious for the other players who are there to learn and grow. You probably don't want to be that guy at a blues jam. It's not gatekeeping to tell you that before you embarrass yourself.
I am definitely in the learn and grow stages - I do a fair job of passing myself off as a blues bassist when I have half a clue as to what's coming up next, but there's a lot about the historic roots of this music that I don't know. So I try to stay humble in those rooms and listen to what's being played so that I gain some familiarity with it. I do have some chops, so I get to go up with some of the better players sometimes, but they'll also stick me with the less experienced players because I'm tolerant and there to help, and they know I'm not in the same league as the hall of famers who show up.