I grow lots of different types of tomatoes every year and get huge crops. As they always go in fresh soil in big pots, I never bother fertilising. I have in the past, but it never seemed to make any difference.
I water once a day as they are in lots of soil in terracotta. I find all plants dry out quicker in plastic posts.
It is worth pulling off the additional small side shoots as that is just a drain on the plants.
I grew some this year we just popped them in a grow bag and left them to grow. I seem to remember someone telling me you have to nip the flowers off but don’t quote me
The flowers are the tomato fruit .... do not remove - they will flower and bud - a tiny bud will start to grow once the flower petals have wilted and started to drop. At this stage water twice daily- make sure they are well drained - the grow bag is a fantastic idea but one of the easiest ways is to top off the top of a bag of compost and stand on its closed end.
Its best to fertilise daily - but only when your plant has developed fruit.You can use fruit or veg fertiliser and liquid works better.