I think you are interpreting the sensitivity correctly, and 8.9 isn't great, but it isn't the worst either. As you found out, this falls between the published specs of many more commonly used microphones. The JB3 can provide some gain to compensate, but it may be noisy. I would recccomend saving up a bit more and buying a UA5 or the GP preamp. I don't think you're going to be blown away by the sound of B2>Art II regardless of the sensitivity, but if you want to start with small diameter cards, this will work.
If you are planning on going B2>Art II>Hosa 176>?adapter>JB3 you are going to need a mic stand, T-bar and XLRs which is going to run $400. If you have fun recording, I'll predict that you start trying to figure out what you're going to upgrade next and then you'll regret buying all that stuff instead of saving up a little longer and getting something a bit more commonly used.
Just out of curiosity, did you consider a stealth style setup instead? It might be a little cheaper, sound a little better, be easier to run and you might not get the upgrade bug as quick either. Of course all of this is just my opinion and I don't think anyone on this board has tried this setup, so it may work out great. Good luck, +T.