A common mistake that people make when trying to design something completely foolproof is to underestimate the ingenuity of complete fools - D. Adams, 2009.
You just go to team then players then contracts, there you can fire players or give them a new contract. I wouldn't recommend you to fire players though, it's always better to sell them.
It will depend on the people you're playing against, and how good they are. FC teams is really easy to beat, since they're not managed by any manager, therefore they do not improve. The higher your division, the harder it will be.
Yes, this is true kick and rush seem to be the best tactics in this game. This two are the best formations aswell, 3-4-3 is more of an attacking formation and 4-3-3 is more of a defensive formation. The attack is very important in this game. If you have midfielders with high shooting and heading you can put them on offensive and it will add alot to your attack, you'll be able to win more matches. The midfielders with high passing and playmaking you can put on passing, it's all in Idividual (individual orders), you can see it when you set up your line-up next to "selection in formation". It will really help out your team. I hope I answered your question.