LOL nice fleet.
Computer always runs when you have a bigger fleet, but will stay and fight if you have a smaller fleet. What it doesnt do is realize if you have 3 repair stations, several hangars, and a small fleet, you can chip away at their fleet for a long time before they decide to run.
Easy defense tips. Always have 2-4 repair stations, recomended 3 that are on the edges of each's repair radius. Put all your hangars, lrms and light carriers inside the area that all 3 repair places cover. Upgrade repair stations to maximize 40 hull points a sec. Surround this fortified area with the defense cannons. Make sure the canons can reach the 120 - 180 degree arc the AI attacks your planet at with its siege frigates. As soon as you can get phase jump disrupter, put it on every edge planet. Fill remaining tac slots with hangers, should be 3-5.
I love using the marza as my defensive capital. He can really pick off frigates fast with his nuke and autocannon extra damage abilities. It is ideal to have a good 30-50 fleet points laying around to fast build a small fleet if you get surprised. If you have a defensive sweeping fleet, make sure they only have to cover 1 phase jump away from a central defensive planet. You dont want to be more than 2 hops away at any time.