Hello John
Rigid forks all the way if your journey consists of what you've describe above, but I'm sure the Vulcan comes with lock-out forks, if so then keep them this way it does help.
Rather than throw a lot of cash at your bike (like I did) it might be worth considering looking for a cheap second hand hybrid or rigid framed bike, or even check your local scrap metal merchants as they seem to get loads of bike frames you could rescue a pair of rigid fork from, for a few quid or even a whole bike for that matter.
you should see the difference with the road tyres you've switched too, I've Specialized Nimbus fitted to mine, but run them at 70 psi front and 75 psi rear 10 / 15 psi above recommended.
Good luck with your choice
Norm