I didn’t do a good job of pollinating them, and only had an overall turnout of about 50 percent of the flowers that bear fruit now. I fertilized twice, the first time when I was reporting the seedling, and the second time a couple weeks ago. About 2 months apart.
Tomatoes pollinate themselves, it's unheard of for pollination to be a problem.
Fruit set is another matter, as it only happens at certain min-max temperatures. Has it been either unseasonably hot or cold?
Fertiliser: this is most likely to be your problem. Feed twice a WEEK with high potash feed, comfrey tea, seaweed extract, and work in a little woodash to the soil around the roots.