1. Currently the default is 600 points in each crafting, combat and minor skills. For every point in Intellect you can get 1 extra skillpoint. So the maximum at the moment is 700 skillpoints, but most players invest in other Stats then Intellect and keep it at 600. As investing points in Stats like Strength and Agility are currently more worth it then Intellect.
Currently in the YO any server can set its own skillcap. It can go as high as 3000. On those server you can have any skill at maxiumum. The idea of 600 skillcap, is so that you need a group of players to build a settlement instead of doing it on your own.
2. Haven't played Wurm, can't say. Just that LiF is more combat/PvP oriented, more guild vs guild. While Wurm is more PvE and has a deeper crafting system.
3. There are some 'official' servers but these are all abandoned. Everyone plays on private servers up to 64 players. Many guilds and servers are recruiting new players. So just join a server and type in global or apply in any of the recruitment topics to find a group to start out with.
Question 4. - 6.
I'd suggest you take some time to read the Wiki. It holds this information in detail.
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