Knee high by 4th July is an old saying that applies to feild corn. Back when this was common, it was open polinated feild corn not hybrid. Now I don't think there is any open polinated feild corn planted. Now corn planted early will be tasseling by the 4th. A lot of sweet corn is mature at about 4 ft. Longer season varieties can be 7 to 8 ft when mature. Feild corn is bred to produce stronger stalks and increased yield. Some of it is high starch corn and usually not mixed with other hybrids in storage.

Not sure, it probably won't do anything. My corn last year grew only to about waist high for some of them. I got only a couple baby cobs with some pollination. This year I hope it will be much much better.

You don't prune it, do you? How big was it when you got it? Was it a little whip or hardly branched? Less than specimen plants when bought sometimes take that much longer to get where you want them to go. Are there any plants near it that would cause a lot of root competition like a maple? Is the growth at least lush? If it is lush, I would leave it alone for now. I wouldn't worry about half sun. I have lilacs in less that bloom beautifully and so do my neighbors. That can explain the extra time it will take for yours to bloom. Of course, more sun, more blooms. When we moved here, my DH and FIL took it upon themselves to cut down some old lilacs, not knowing what they were. It took several years for them to bloom again, at least three to four, maybe even five. I would worry more about the clay. You should be able to tell if it has wet feet just by poking around a bit. Being this is your third year, it might just take off this season. If not and you dig it up, you will be able to tell by the roots if it hit clay dead pan. Maybe they are curled around or cork screwed and need to be spread out. Then you will have to break up the ground beneath it. Pick axes are great tools. Maybe the roots are still small, not growing well, not spread out into the soil for whatever reason - pest or disease. If you are not getting much growth on top, I would guess this to be the case. If you shovel around it and the plant looks like it is going to come up easily, I would move it now. If the roots are real small, I would let it spend some time in a large pot with some nice potting soil like miracle gro and let the roots get going. Then all things being seemingly equal, sometimes a new spot does the trick, sometimes a new plant. Good luck!

***, I saw that he had gotten off the tractor and was motioning at something in the fencerow. As I pulled up I saw a dark blob in a bush and somehow I just knew it had to be more bees. Now he was finally excited. He'd never seen a swarm before and I still tried telling him that this little pile of several hundred bees was nothing at all like the previous *** Cool! We had a swarm just hanging--about the size of a basketball--in an evergreen in the front yard of a farmhouse in Central Iowa. It was fascinating and slightly nauseating, at the same time...if you catch my drift. I had two small children and I was afraid they'd get out of the house and head toward the noise. I believe bees "swarm" either when they find their hive uninhabitable (for whatever reason) or because, as you said, they have an extra Queen and need to separating the fighting aristocracy. :-)