Cat5e should run at Gb speeds. And, the cabling is usually never the bottleneck. First, and I have never experienced this but delete all of your deletions and orders. And, of course, run the tools in AC.
How much RAM do you have on your main computer? It may be that SQL Server takes more and more RAM throughout the day. This makes SQL faster, but it can take up all the free RAM for the system. The connection string for AC to SQL is not ideal as it isn't set up the way most databases are, hence the slow login. What type of WIN 7 do you have?
When you first reboot the computer, check Task Manager (Performance Tab). Not CPU Usage and amount of Memory being used. Also look under Physical Memory (MB) and see Total memory and Available memory. When it is the slowest, check again. Then note how much available memory you have.
