Front set/headtube feels sticky

You need a new headset. What's happen is that there is a fine flat spot being worn along the center (which is where things are most often lined up). You can loosen things up a little bit to get feeling right again, but you need a new headset. My old Litespeed Tri bike did the exact same thing last year. I put a new fork on it and like a few weeks later the old headset did the very same thing.

+1 on needing a new headset.

For the time being, you can loosen the headset a little (just a TINY bit) so you don't have the self-centering bump there.  Make sure it's not too loose such that when you hold the front brake tight and push the bike forward and backward against the brake (but the brake is of course keeping the bike still) there is not bump or knock felt.  If there is a bump/knock when you do that, the headset is too loose - try again.

Of course I'm used to working on my threaded headset and I understand how to adjust that.  I don't have any experience tightening/loosening a threadless headset which is probably what you have.  If you want to DIY, try the Park Tool website for instructions.  I've also found "The Bicycle Tutor" (google it) to have helpful videos, etc.

Good Luck!!