size of fleets midgame

[minipol]

I'm in my first simultaneous game agains the AI and i like it more than turnbased. Especially the repeat orders is very neat for satellite and mine placement.
Anyway, i blocked an AI (forgot the name, they are orange beings) in a corner of the galaxy. They only have 3 systems. I invaded with a fleet of 29 ships but it had some support ships like AA, supply, minesweepers, repair ship, troop transport.
My fleet was destroyed by what i thought was a harmless planet to start my attack with. It only had about 140m inhabitants so i thought it was going to be a piece of cake

Of course, it might have something to do with the orders i gave: capture planet.
I have 2 assault troop transports ( normal transports with shields, armor and a beam weapon )
in the fleet that where supposed to drop their troops.

Now for the questions:

1. Is there a way to replay the combat in simultaneous?

2. What's a decent size of a fleet for midgame attacks? My fleet included about 4 missile ships
( missile IV ) and 12 beam ships (APB VI mostly).
As it seems, this was not enough.

3. What's the best way to test if a fleet is going to do the correct thing? I now use the combat simulator to achieve this.