it just looks like it lacks vigor to me. weak structure/growth.
stuff you get from the grocery store are essentially first generation hybrids and their offspring are going to be garbage. the only exception to this is if you buy what are referred to as "heirloom" varieties here in the US, but typically you're only going to find those at like farmers markets, and only sometimes.
if you want to grow some vegetables, buy some seed. if you want to get into seed saving, buy heirloom seed and save that.
like not burpee, because that's like the WalMart of vegetable seed. overpriced and shit quality. terrible germination rates, just across the board crap.
nationally, Johnny's is fine and ships/sells in small packs. look up your local cooperative extension service for recommended varieties in your area and other growing practices associated with those varieties (suckering? determinant? trellis style?), seed a flat of them and then plant them out after the recommended last safe frost date.
No problem, damping off has claimed several of my cannabis seedlings in the past
A lot of commercial crops are grown from plants modified to produce no viable seeds. If that's not the issue you could always try starting them indoors and then moving them into a bed once they are stronger.
I suppose tbh I don't actually know the mechanism by which those seeds are produced. That's why I suggested starting them in an enclosure of some sort. Not even necessarily indoors but even putting a mesh cage over them, It could also be any number of other factors. I've only grown from starts.
Genuinely could just be wind cutting them down. Start your seedlings indoors and transplant them outside when they're sturdier
Slugs and snails will do this. Had to replace all my cucumber seedlings and put down stuff to control the slugs/snails. I started spraying down my plants with "inscticidal" soap spray. It's less harmfully to bees and other pollinators. I usually don't have trouble after they get past the seedling stages. A few occasions I actually went with legit insecticides at the very start but normally I don't have to go to those extremes.
Also in would suggest not using seeds from grocery store bought tomatoes. I did this and they came out tasting... Well like store bought tomatoes. Get some heirloom seeds Or, if you have any farmers markets or other sources of locally grown foods use seeds from those. We have some Amish vendors that set up locally and their tomatoes taste a hell of a lot better that store bought.
If the plants start getting too tall, clip the top off. They will grow bushier and if you trim areas with no flowers it will focus more on flowering than vegetative growth too.
Also tomatoes need a relatively large root volume. I would give 1 tomato plant at least it's own 5" pot.
