Hey there! Let me start by saying that I am glad you have found some success and relief with the Keen shoe brand. I almost exclusively wore Keen for many years. Sad to hear that the HOKA’s weren’t a great fit for you, as I also love that brand! But that is enough about me. Let’s answer some of your questions.
1. In terms of fit....for many years I found Keen sizing to be tricky. Sometimes I’d go a half size up or down depending on the style. I do not find that to be the case anymore. I think trying the same size you have in the boots would work. The only exception to this is if when you were fit for the targhee, you knowingly increased your size to account for something like foot expansion, or to accommodate a heavier sock, or something of that nature.
2. We of course can’t truly confirm what will be best for your back injuries. We just aren’t trained to give health advice. However, some tips would be to look for the same attributes in a shoe as the one that you have had success with. For example looking for the same type of footbed as described in shoe descriptions or looking for the buzz words that indicate it won’t be a good fit for you. In the case of the HOKA’s it seems that it was that type of rocker bottom, so I’d say it is safe to stay away from anything that alludes to that type of technology.
3. Let’s talk about ASICS! Great shoes for many. If you are looking for comfort and stability take a look at the ASICS Gel Kayano .
4. Lastly, we look forward to seeing our customers again too! Also, please if you find something that really works out for you, please let the broader community know!
Hope this helps or at least gets you started in the right direction!