Hey guyyss!! Had another session with the book today, and played a few games, i think i can now answer all of your questions.
First off, assault weapons cannot fire like defensive weapons, neither can template weapons. No distinction is made in the vehicle rules.
The rear armour rule is there. When assaulting a vehicle in CC you hit the rear armour.
If you assault a vehicle in your go and dont destroy it, you may attack it in the next CC phase, ie your enemies, if the vehicle does not move. You can be shot at by the enemy however as you are not considered locked in combat.
Skimmer rules: Fast skimmers may move 6 inches and fire all weapons, or 12 inches and fire 1 main and all defensive weapons. Skimmers may not move and fire all weapons, or move up to 6 and fire one main and all defensive weapons.
Fast SKimmers may move flat out ie 12-24,fast vehicles may move flat out 12-18, and gain a 4+ obscured cover save. There is no save for a skimmer moving less than 12!!!!! These are cover saves, so cannot be gained against template weapons, crack shot, markerlights reducing it. etc. Works like a normal cover save. Can by fortuned btw.
All vehicles are hit automatically in CC if they didnt move, on 4's if they moved up to 6, 6's over this. This means skimmers that dont move are hit automatically!! on the rear armour.
Smoke launchers give you a 4+ cover save for next enemy shooting phase.
Blast weapons that get hot: Roll a dice for each weapon before firing. On a 1 you do not fire and take one saveable wound.
Rapid fire gets hot is gone. You only overheat on 1's to hit, not 2's.
Feel no pain cannot be used against instant death, AP1 or AP2 weapons, power weapons, rending that rolls a 6 to wound, etc.
Twin linked weapons. Twin linked blasts, you must choose to reroll the scatter and the 2D6 or none. Twin linked gets hot only overheat if the second roll is also a 1.
Snipers: always wound on a 4+, rending, strenght 3 against vehicles. THis means you use your BS to hit.
Scoring units: all units from your troops allocations on the FOC are scoring, unless they are a vehicle, swarm or have another special rule that specifies they cannot Ie tyranid gaunts who are lurking. The unit is scoring, so one man out of a 10 man tactical squad is still scoring. ANY UNIT may contest objectives.
All units that are not vehicles can run, with the following exceptions :Bikes, Jetbikes, Artillery. Walkers can run. This means tomb spiders, talos' etc can run...hmmm.
Ramming does not have a maximum strength. Nowhere in the book does it state that ramming is limited to strength 10. A vyper with star engines can generate a strength 12 hit it takes a strength 12 hit too btw.
Wound allocation is simple. You do it unit by unit, all shots of one unit on its target.
So using the example above the 3 tyranid warriors, 1 with venom cannon, 1 with devourer, 1 with rending claws are wounded by 5 bolter shots, 1 lascannon shot and 1 plasma gun shot. The player controlling the warriors allocates the 5 bolter shots first, placing them one at a time. You can only allocate a second wound once each model in the squad takes one. The warriors have a 4+ save. Two take 2 bolter hits and 1 takes 1 bolter hit. Now the plasma goes on the warrior who was hit by one bolter shot, and the lascannon on any warrior of the players choosing.
Now roll saves. The first warrior who has a venom cannon is only hit with 2 bolter shells and makes 1 armour save. The second warrior is hit by 2 bolter shells and a lascannon shell. he fails 2 saves and dies. The lascannon hit is wasted. The third warrior makes the save from the one bolter hit, and takes one wound from the plasma.
I was used to the system after one game. Its easy to learn. Works the same in combat also.
Combat: Units that are charged get a free 6 inch counter assault move to get them into base to base if possible. Casualties can be removed from anywhere in the combat, not just the 2inch killzone. Models who are able to attack at the start, before any dice are rolled, still get to attack, regardless that all the models in the killzone were killed before they got to attack.
Combat results: Models killed vs Models killed. today in my game my conscript platoon was charged by 5 terminators and a wolf lord. They killed 12 conscripts with no reply. I lost the combat by 12, but i am fearless due to Gaunt, so i take another 12 armour saves!!!
If i wasnt fearless i wound have autorun, except on a double 1 for insane heroism.