I'm also a new player, and play exclusively imperial, but I love the ISD, so what I can tell you is what I dread most when facing a list like yours:
You have more ships than him. If you pick objectives that favours splitting up your fleet, and deploy at extreme range, he will have to decide what to eventually take down and commit to one side. That way, not only can't he go for VPs, but also doesn't have enough turns left to flat out table you.
If the rebel starts slow and jumps up his speed later, he, on the other hand, can potentially focus all firepower on a single target, which not even an ISD is going to like. Also, TiEs hate being in enemy flak. If the big ships are straight up ignored, those 3 hull squads tend to go down in droves when focused down.
If there is a rebel ship that isn't finished off, it's likely there won't be another round of effective fire once it shot past the imperial ships. This means going at the rebels in a staggered line so far worked well for me, as I could mitigate this somewhat, but a ship that scored and than almost died does not care that is has only one hull left when the game ends.
Tl;dr: From what little games I played, my greatest concern as an ISD player is commiting too early to one side of a fanned-out rebel line, as it can still pounce a single ship very effectively. Staying back and goading an imperial to do just that usually presents the rebel important openings.