@scott-williams First, I’d recommend you use a binder like Sure Gel or Super Bind or a moisture retender like Carrot Fiber. This is always the first thing I recommend when someone has an issue with the texture of their sausage.
Your fat content is correct and it sounds like you used the correct amount of seasoning. 190° is a little higher than I would recommend, but we have all been there when it’s just taking too long so you dump it a little more than you really should! I don’t think that is the issue but check out this post titled Summer Sausage Nightmare specifically @Parksider’s response to finishing it up in water. It’s a good tip and I am going to be doing some tests on it here to verify a few things.
What I think probably caused your issue was the mixing in some way. When adding pork fat to your venison I think the best time to add it is during the second grind, it’s possible that your fat didn’t really mix in well with the venison, that would explain why it seemed dry even though you had the correct fat content.
It also could have been lack of protein extraction, I looked through your posts and can’t tell if you have a mixer or are mixing by hand? With cured sausages, I always recommend using a meat mixer as getting the right level of protein extraction. I am guessing that you had some fat out where the fat renders and cooks out of the product.
Hope this helps!