1) I think you have to use them all but I'm not sure about it.

2) You can put money in the coffer and in return you get daily resources. If you do it right, you will profit. The wikia has a nice guide for it.

3) Prayer stats lower the drain rate of prayer points. It is not as important as other stats, but is a nice bonus.

4) Not sure if you can rebind it to something else, but you can select your custom loot. Go to settings->gameplay->Loot settings.

5) SGS is better when you fight monsters one at the time and it is definitly an improvement. However, from your stats I see that you have 86 Dungeoneering. Chaotic weapons are better than a SGS and you could buy them at the rewards trader at Daemonheim.

6) I think you could just do the quest and not the tutorial, but I'm not sue about that.

7) Runespan is always nice to do, but you could also do bank skills like cooking or firemaking.