3- Assassin's kiss skill, that uses backstab, makes me confused lol. Do i have to be behind a target to get the ability to trigger?
I can't answer all those questions but I got a handle on this one. How backstab works is you just attack like normal. The more points you have it back stab the greater % chance you have of doing double damage. When the back stab damage is applied, you will see the work backstab just under the damge applied to the monster. Maxed out back stab gives a 50% chance to do double damage. So the net effect is a dagger is then doing 150% of its listed damage.
The best daggers in the game have a range of about 47-63 damage. (A little higher for non magic weapons) Compare this to the best one handed swords which go 71-100 on the uniques and a bit higher in non magic weapons. Swords however can get no additional damage from spells only greater % chance to hit and speed increase. So a 47-65 damage dagger will give an effective damage range of 70-94 which the backstab modifier. Similar damage to a one handed sword. The dagger with the best potential is the one from the Holy weapons quest. If you save before you identify it, you can reload to get better mods on it.
My warrior class is using a dagger. Of course the warrior is better at melee not just because of higher damage from strengh points but because of the whirl speacial attack which will hit all close targets instead of just one.
From reading other posts I believe scorpians is one of the favorite traps of survivors. I tried them out with my warrior and with only 1 point in the deadly gift skill they over power the imps in the wasteland. If you place the Aura of command skill on a scorpian it will follow you around and attack who you attack instead of running around randomly. I don't like them much because they seem too strong for just 1 skill point.
There are multiple ways you could play a survivor. Keep in mind that all 3 classes could be made into casters because the merchants in the market place and Verdistis sell silver charms early in the game and gold ones will drop in the last 3rd of the game. It takes awhile to get enough money to buy them. With charms and equipment even a warrior class with no points in constitution can get 600-700 mana around level 25ish. Not all games go the same, sometimes the merchants sell strength charms when you need mana.
Some dangerous quests can be done earlier by using shadow potions or the fade from sight spell. You can do missions behind enemy lines this way.
Skelatal wall can help occupy baddies while you cast. Life leech is great for the Elite orcs no matter what class you use.
Don't know if any of this helps. I have noticed that monsters in the wasteland (last part) have around 75-100 resistance so elemental spells don't work as well then but the curse spell(there are two, the one in the survior tree is better) will lower there resistance. Hell spikes are good because monsters have no resistance to them as they are considered a physical attack.
I suggest saving your game before you add a new spell. Then try the spell, if you don't like it, reload your save and select a different one.
Edit- I stated swords can get no additional damge from spells. I meant physical damage. There are of course the ones that add elemental damge but these can apply to any melee weapon. The elemental ones that add poison, fire etc help more in the beginning of the game and not as much later on.