Tricky without knowing which fork it is but here goes....

Presuming the right knob is not a cap, but is an adjuster, wind it in or out, and see what effect it has on the damping. Have a look at the bottom of the right leg, if there is an adjuster there do likewise to stiffen things up.

Wind the preload in (+) as far as possible.

If this sorts it out then great, if not either replace the forks with rigids or if your bodge mojo is strong then replace the spring with something solid cut to the right length, or fill the right leg with oil to the top, creating a hydraulic lock that will fix the leg at full length.

Slicks and (if its hilly) bar-ends, maybe cut your bars narrower for easier filtering through stationary traffic, SPD's if you aren't on them already.

Can't think of anything else, apart from buying a cheap road bike!