The only place to put silicone would be in the holes in the deck flange where the crossbar mounting bolts pass through. This is to prevent water intrusion into the hull in the event that there are any voids in that area that could let water into the hull. I have never really found this to be necessary, but some people do it. If your hulls leak, it would be a good place to start.
As far as bedding the crossbar saddles in epoxy, some people have done this. Again, I really don't think it's necessary and the performance advantage is questionable. Just make sure your crossbar bolts and your trampoline are tight and accept that these boats have some flex. The H18 just doesn't have as beefy a crossbar as some of the more modern boats and the end castings and hull connection system all allow for some slop to develop.
If it were me, I'd just clean all that old silicone off the crossbar. Reassemble the boat (be sure to use anti-seize grease on all the crossbar bolts), and make the tramp good and tight. Re-tighten the bolts every time after the first couple sails and you should be good.