Catspin:
It would be nice if there were some formula for winning races, but there is not. Racing is warfare, and battles are always fought differently based on the situation. "Situation dictates."
It always boils down to how bad you want to win. Let's say you have a field of 60 riders on a one kilometer course. Every rider there has a 1 in 60 chance of winning statistically speaking, but in reality there will only be maybe a handful of riders who will be agressive and smart enough to win. The rest want to win, but they will be racing without any goal or objective. They just show up, pay their money, and ride in the pack until the race is over.
If you want to win your races, you have to want to win badly. Since you have 2nd and 5th place finishes, you have the agression to win for sure. Society teaches us agression is a bad thing. Agression is mandatory for racing however.
Positioning is critical. You noticed the winning break 100 meters in front of you. You must mark your competition and never let them out of your sight. Team tactics are much more difficult at the 4/5 level, since inexperience and upgrading "greed" are rampant, and rightly so for the most part. Who wants to get up early, pay money, and work for someone else, helping them move up to a faster category while you stay in a slower one.
If this is not a problem for you or your teamates, get organized. Cover breaks by sending one of your riders up to the break. Rally everyone up front, and send a man off the front. Have your team block the race by riding just a tad slower while your man gets a gap. Block by taking longer lines around the corners also. Find someone who can ride super fast for 30-60 seconds and have them lead you out. Just before your leadout man blows, sprint for all you are worth. Ideally he will get you to 200 meters or less from the line, and at a speed well over 32 mph. Whatever you do, do not attemt to sprint over 200 meters. If your leadout man drops you off at 300 meters, you are probably screwed.
If a break goes near the end, it is mandatory that you and your leadout man make the break. If you are a feared sprinter, the break may just stop working. Why should they tow you to the line so you can crush them in a sprint??? Of course, you should do as little work as possible yourself. There is a fine line between being a wheelsucker and doing too much work.
If your team is up front at the end (it should be) and your leadout man gets you to the line first, it's possible to place your team very well, maybe 1-2-3 or better.
Decide that you want to win the race and that you will win the race. Get your team organized. Decide well in advance what each riders role will be. Develop hand signals to communicate with your teamates. Make sure everyone knows what the race strategy will be, and make sure everyone rides and stays up front the whole race. Some team will occupy the space at the front of the race, why not have it be yours??? Someone will win the race, why not have it be you???
Make a list of all the races you are going to do this year. Write down all your goals for the year with regard to placing, a "macro" view. write down on a piece of paper something like " I will win the "xyz" criterium on saturday," as the race gets closer, a "micro" view. Write it down several times. You can also write out things like "I will make all breaks" "I will win all sprints," etc. It is important to physically write these affirmations on a piece of paper, not type it on a computer. There is something very special about the physical act of writing. Writing down your goals is so important, but most people don't even think of it.
Try these things and see if they work for you.
Good luck!!!