1-2. There are restrictions on signatures, based on your activity/rank.
- Newbie: No styling (including links) allowed. Max 50 characters.
- Jr. Member: Links allowed. Max 150 characters.
- Member: Unlimited length.
- Full: Color allowed.
- Sr. Member: Size allowed
- Hero: Background color allowed
3.There is an online table generator like this one:
http://truben.no/table/ you can generate tables in bbcode then come back here and try to post a reply and click preview, so you can see the output how will it look like, then you play with colors etc.., maybe the designers have other tools, wait for their replies.