I would try what your dad said, but I would also transplant another cherry tomato seedling into a second bucket. I think it's too late to start from seed in your zone, but a large transplant should be ok.

Tomatoes need 6-8 hours of sunshine a day BUT you are in Texas so I just don't know what people do in your area because of the heat. Without enough light they get lanky and foliage looks more sparse. You do need to water containers quite a bit, even everyday if it is hot, but I found that some potting mixes do hold water more so until you know for sure about your mix , I do think a cheap water meter helps. And eventually no matter what you do they are going to start declining as they age. I believe you can plant again for a fall crop but someone from Texas would have to help you on that. The fertilizer in your mix would have long been used up and containers need fertilizer--just think- you water every day so you eventually don't have any nutrients left at all. WIth no fertilizer that plant had nothing to nurish it and make it a grow. As to what type and how much--there seems to be as many answers as there are people who grow in containers. You can use time-released (dynamite), Miracle gro (follow label), homemade compost, EarthJuice, Espomo products (see web site), natural fertilizers, fish/seaweed emulsion, etc, etc. I use the latter-- the natural and fish stuff but am going to try something from espomo too as alot of people like it. I also put dolomite in the mix-1 cup in a very large bag (75 quarts). If you can swing it--(cost $40) an Earthbox is a great product for the beginner. Fertilize once and then water through a tube, impossible to overwater or mess up. I have 7 but I also have about 30 -15 gal. containers. and 6 - 50 gal. ones. I also always mulch the containers. If it was a cockroach you saw-don't worry about it. You find them alot in compost. I don't know about the cut stem and what you saw but remember you first have to grow healthy plants or you will see all sorts of problems develop with stressed and unhealthy plants. Good luck and remember you learn alot every growing season.

I think it's plausible that a different rootstock might subtly affect how certain traits manifest. It might increase or decrease production or affect fruit size, texture (due to water differences), even flavor of fruit. We know that rootstocks can definitely affect the quantity and quality of foliage. Why not fruit? Yeah, genes are genes, but epigenetic influence can be significant, and a different rootstock does change the exposure of the scion to environmental factors having to do with nutrient/water uptake and circulation. While I'm sure that any effects that do exist would most likely be minor, it's not as though there's no plausible mechanism for the rootstock affecting things like taste, production of fruit, etc. I'm sure a lot of those possibilities will be studied if tomato grafting becomes more practiced commercially. I wonder whether there is a body of research on it in other countries that have practiced widespread grafting for much longer which is not available internationally because it's not in English. EDIT: Grafting effects on vegetable quality "Most reports on grafting suggest that changes in the scion are controlled by the rootstock through controlled uptake, synthesis, and translocation of water, minerals, and plant hormones[...]A few studies have explored how the scion is affected by mRNA and protein migrating from the rootstock. [Some researchers] showed that mRNA and [...] phloem proteins from the rootstock can migrate from the rootstock through the phloem to the scion and accumulate in the phloem and apical tissues. One of these mRNAs is a member of a gene family in which some the members are reported to be involved in apical meristem development[...] Another was shown to change leaf morphology of potato scion when grafted onto transgenic modified tomato rootstock. Tiedemannand Carstens-Behrens (1994) studied the phloem proteins that differed in cucumber (C. sativus) grafted on figleaf gourd (C. ficifolia) or on pumpkin (C. maxima). They found four proteins on sodium dodecylsulfate polyacrylamide gel electrophoresis gels in grafted scions that do not appear in control plants but matched the rootstock phloem protein pattern. Two of the proteins match the phloem protein 1 and phloem protein 2 molecular weight of the rootstock. Ruiz-Medrano et al. (1999) suggest this migration is a novel mechanism likely used to integrate developmental and physiological processes on a whole-plant basis. The phloem proteins role may be in long-distance transport of RNA within plants[...]"

I ended up with a cherry fort - not a maze. The signif other decided to downsize the whole deal... so I ended up with a 10 X 10 area. We were starting with lawn... So I planted a tomato every 6-8 inches. I know inches... I put in: Gajo De Melon Suncherry red star sungold green doctors zebra cherry black cherry snow white Riesentraube OSU Blue Oh heavens, I'll have to go home and check again... there were others... I got a lot of people who wanted to donate seed, so I took them up on them and added them to the 'fort'. I have to take recent pictures, but this is what it looked like early on. I haven't been gung-ho on documenting this because I didn't want to document a complete failure if it happened... :) Then I went back to the original farm (without my camera) this weekend and they have extended their tomato maze - lots more varieties and much bigger this year... I will bring the camera next time I go. Again they told the kids "come back with your basket and belly full." SO cute and SO gets them excited about gardening. I want that!!! I'll take pictures tonight and post them tonight or tomorrow.