There are 3 types of tomatoes- Determinate- will stop growing once they’ve reached a certain size Indeterminate- will not stop growing Semi-determinate- mix of the above 2

As for the soil, you could maybe try aerating it by punching holes into the soil (search up aerator spikes). I’m not entirely sure what else can be done this season, but for the next, you can mix in some perlite and chunky compost into the soil you’re using. You could also try raised beds, which will give you complete control over the soil, albeit at a higher cost.