First, when a spore impacts an eldar ship, does he get a holofield save on a 2 plus? The errata says can save vs damage on a 6 plus. So I am thinking it ignores the holofield entirely.
On planetary assault some of your ships start in low orbit. I cannot find the rules for moving out of low orbit. Is it a move action to leave low orbit or do you get to move your move straight from the planet?
I don't know the answer to the question on tyranid spores.
As for the second question, I suggest you read the planetary assault scenario again. The defender's ships either start on patrol on in high orbit - it doesn't mention starting in low orbit.
If you're still interested in low orbit, though, check page 46 of the rulebook.
"A ship within a planet's gravity well may elect to enter high or low orbit. A ship does not have to move whilst it is in high orbit, but such a stationary ship uses the defences column for gunnery purposes if it elects to remain stationary. A ship that enters low orbit, however, is removed from play and (where the scenario requires it) is placed on a seperate low orbit table. Ships moving up from low orbit are placed touching the outer edge of the planet template."
Page 48 of the rulebook:
"If a ship in low orbit moves off the table from any other edge, it is assumed to have left low orbit and is placed back on the main table, tounching the edge of the planet."
For your fleet list: remember each hiveship must have escorts.
From the 2010 FAQ: "The fleet
must have at least six escort drones for every hiveship in the fleet. If desired, this may be in addition to the 6-12 escorts (of any type) that may be taken for every hiveship in the fleet."
I see 45 escorts in your fleet, but only two hive ships. Shouldn't there be a maximum of 36 escorts in there, of which a minimum of 12 must be Escort Drones? Maybe I'm just showing off my ignorance of campaign fleet composition. The last bit is the most likely.
Advice: Vanguards are useful for "marking" enemies, allowing ships to fire at targets even if the target isn't the closest target in range. In addition, you can't fire at ordnance unless a vanguard drone is nearby. It makes sense to split them up into several squadrons to cover far more space than a squadron of 10. A squadron of 4 would be 100 points and a squadron of 6 would be 150 points (and allow you to deploy them in convoy games, where escort squadrons usually aren't allowed to be more than 100/150 points).
Bio-plasma is very cheap, and very useful against high-armoured targets. A small squadron of 6 escort drones with bio-plasma is only 90 points - they don't need to worry about placing blast markers on ships (reducing the accuracy of the pyro-acid batteries) or firing through blast markers already present. I do think you need some bio-plasma to deal with the marines (or imperial front armour), and at 90 points they could appear in convoy missions.
Replacing a massive claw with a boarding torpedo launcher would add 5 to the points of your cruisers, but make command and control slightly easier. It would reduce your claw damage, though. I don't know if it's worth it.
As for the kraken: your kraken are the only fast, agile ships that can be armed with powerful ranged weapons (like pyro-acid batteries). Vanguard get strength 2 batteries, and drones can only turn 45 degrees and move 15 cm. Your cruisers can get good pyro-acid batteries with good fire arcs, but they are slow and turn even slower. It would be useful to have a squadron or two of ships than can chase down escorts. Vanguard drones with feeder tentacles might be good (except against eldar), or kraken. I therefore don't think it's a good idea to bunch all of your kraken up into a single squadron - you need more tactical flexibility so you can allocate some ships to anti-flanking duties while putting the bulk of your forces into an attack.
Lastly: The increase in the number of squadrons could strain your command and control capability. Maybe add a third hiveship to help with that? Maybe. I'm not sure.
EDIT: Eugh. I'm clearly not good at being concise.
EDIT again: How did I forget to mention fireships? They're very cheap.
... They're also fun to watch when you blow up half your own escorts, but fun is good. Since fireships can be placed deep inside your escort squadrons to protect them from fire there's a good chance that the enemy would have to deploy ordnance to destroy them. Massing spores could help against that, or just flying a cheap escort drone into large squadrons of bomber. Just remember that fireships only move 15 cm and can damage things up to 18 cm away, so it's very easy for you to blow up some of the rest of the squadron if it's a large squadron and the fireship was at the back. If you're anything like me, though, that would just make things even funnier.
