I think you should try out a different bar/brake setup on your vintage road bike first to figure out what's causing your discomfort and if drop bars will be something you find beneficial or not.

I've done a drop bar conversion on a MTB and there are some tricky aspects to it. It was a fun project for me and made less expensive by the fact that I had some surplus parts like brifters sitting around. One of the other things that made it easier was that I had a road bike which fit and was comfortable. That made getting the bars positioned right on the MTB easier since I had something to compare it to.

Since you're thinking of continuing to use the bike off-road I'd seriously consider some drop bars meant for cyclocross bikes. They're wider and flared.