Hey tofast4u05, I am in a similar situation. I'm a good 4.5 player singles player in Norcal, and I win most of my matches at 4.5 comfortably. I was bumped up to 5.0. Having seen your videos, it's interesting because I see a lot of parallels. Like you, I move pretty well and feel like I can get almost anything back. I also feel like my groundstrokes are like yours (loopy/spinny): they don't do a lot of damage but they rarely miss. This kind of consistency and the willingness/patience to play long points pretty much guarantees success at 4.5.
Against 5.0 players, I typically lose because they apply effective pressure by waiting until they get a relatively short ball. They also come in to the net frequently to finish the points after they hit a good shot. They are rarely willing to simply engage in a grindfest (like your Grand Prix final match) where one guy waits for the other guy to miss or screw up.
Anyways, here's my advice for you getting to the next level:
- Any short or attackable mid-court ball, you need to commit to hitting a quality approach shot and finish at net. If your approach shot is not very good, you will get creamed (unfortunately a "good" approach shot at the 4.5 level is a weak approach shot at the 5.0 level).
- hit your forehand with a bit more pace (too loopy right now which gives a good player time to set up), or a bit more variation (some loopy shots, and some a bit flatter).
- hit sharper angles and less straight down the middle of the court. This will produce more short/mid court balls.
- work hard on the quality of your first shot after your serve, this is usually where you can take control of the point. If your opponent hits a soft/weak return, you should definitely not give him a chance to go back to neutral.
Basically, you need to start winning more points by applying effective pressure, and less by waiting for the opponent to miss. Good luck, let me know what you think as I am working on the same things.