Mike,
Moving the keel should be easy enough. Just wire the end of the ribs for insurance. You can reach in the front bead hole with a dental pick and push it forward.
I found the rosin flux paste at a local electronics store in a little 2-3 oz container. Radio Shack would be a good bet. Acid flux is a bit tougher. I had mine from a Brownell's purchase some yrs ago. I bought a lot of stuff I didn't end up using, like the homogenized paste solder/flux in a syringe. I have some in acid flux and rosin flux. It's solder ground up into a powder and mixed in a paste of the flux. Works well enough but not necessary and it's expensive. Just hardware store 60/40 solder with or without flux core is fine. Just keep the acid core stuff for only the tinning and rosin core for joining.
