Do you have a name for the variety of tomato you planted?* As far as the size of the tomatoes not being the same as you expected, the label could have been switched and what you really have are plum tomatoes.* I've seen that happen many times.* From the looks of your plant it needs to be staked.*
You don't say what the weather has been, but if the temps are over 85*F the ripening will slow down as well as the growth.* You will just need to be patient.
When weeding, the best way to make sure you are removing a weed and not a valuable plant is to pull on it. If it comes out of the ground easily, it is a valuable plant.