dang it's an hour now. still got the server busy messege : ( let's see when my messege will beposted....
I used to play FFXI and DAoC for couple years as well

I quit EQ once I started DAoC and I quit DAoC once I start FFXI hehe. And to answer your question.
1. Cooperating and group victory seems to be the main focus of the game. Same idea applies to quests and missions. Early missions and most of the quest can be done solo no problem. But as the game goes on your missions will become harder and harder. I am from bastok and here's some of my mission experience
rank 1 > rank 2 - solo

All I need to do was deliver a few letters, collect sample for Cid, and collect items from Quadav. All are soloable by a level 10 or so.
rank 2 > rank 3 - is to travel to sandoria and windurst to provide help to their nations. the first part of the mission is a simple monster killing / sample collecting which can be solo. The last boss of this part is a dragon, battling in a special boss zone with level 25 cap. If you are higher level, you'll be turn down temporily to 25. The battle zone can only be entered by a group of 6 the most. Anyway, the dragon was easy
rank 3 > 4 - rescue and officer trapped in a tower guarded by giants. Having a friend to go with you help tons esp if they have maps and know the way because the place is pretty huge and confusing. a level 45+ or so can walk safely in the tower without being attacked to that might be a good level to do it easily if you want.
Rank 4 > 5 Boss battle in a boss battle group. level cap 50. fight with a boss skelleton with 4 other minor skelletons.
Rank 5 > 6 - Shadow lord. 6 players maximum. aroung level 55 is a good time to fight him with a decent challenge. Bring good group and prepare potions. Shadow lord is not yet safe to solo even at level 70 (some redmages said they can solo at level 70 but I have never tried)
Ok i'll stop there, you get the picture

highest rank right now is rank 9, and for rank above 7 to fight each boss will require up to 10-15 level 65+ to win. Organizing an alliance to pass missions isn't so bad. there's always people wanting to do them and they will bring friends to help with it.
For LS the link pearl system lets you do exactly what you want

I too would want to get around and know people as much as I can and don't think i can stick to only 1 LS.
2. no. aggressive enemies will always be aggressive. can't make them love you. FFXI got a "fame" system tho. The more you help out people from certain region, the more famous you become and some quests will open up to you.