Originally they had no intentions of putting levels in at all, but they had to because many people would be confused without them. Then they increased the level cap because people bitched that there were only 20 levels in GW1. They have done nothing but bend over backwards to accommodate players with familiar mechanics (levels) and higher level caps (a sense of progression) even when it wasn't in their original design to do so.
Also, if you go into WvW you can level up all the same. You'll get loot drops for your level and equivalent XP. Also, yes if you two want to WvW together and you're level 1 and he's 80 it's perfectly fine to do so.
For A) I'll give you a real example. I played my Warrior in BWE2 with some friends who had just made new characters. I was level 23 and I spent that entire time with them in the lower level zones 95% of the weekend, by the end I was level 40. It isn't 100% efficient compared to on level, BUT not once have I ever thought I was leveling slowly. Also, once you hit level 30 the amount of time to go from 30-31 is the same as 79-80 which mind you is ~90 min on average depending on the player. Also, I was getting loot for my level too. Your power relative to the mobs scales to where you feel more powerful with additional Traits/Skills, BUT your health is scaled down to meet the content around you so while you can feel that you're more powerful, you aren't loloneshotting mobs and you can and will die if you play carelessly, even to level 3 mobs. So yeah I went from 23-40 in a weekend not even doing content that was for my level and I went from 40-44 doing WvW over 5 hours.
One more thing, do note that sPvP and WvW are entirely different things. sPvP is structured PvP where everyone is autoleveled to 80 and given all the best gear and weapons right out the gate for an entirely even playing field.
WvW is a server vs server vs server 2 week match up of sieging and fighting for territory where you use your PvE gear and can level your character in an entirely separate part of the game form the normal PvE world.
If you've becomed intrigued then please read my thread here:
http://www.mmo-champion.com/threads/1058358-Guild-Wars-2-Mass-info-for-the-uninitiated-READ-ME!