1) Post all pictures and updates related to your business on your FANPAGE. Then using your PROFILE visit your page and SHARE the content.
2) Post all Youtube videos to you FANPAGE.
Then using your PROFILE visit your page and SHARE the content.
3) I personally don't use twitter with facebook, except I tweet a link to my page saying there has been an update to it, and occasionally (But rarely) place a status update telling them to follow me on twitter.
4) Mentioned above......
Personally I keep my profile personal and my page for my business.
Your fan page and profile should be 2 totally different things. Your profile should show "you". What do I mean by that? It should show a real person. Have a real picture of yourself and use your profile to establish relationships. Don't ever try to sell with your personal profile. It's a turn off. Just build relationships and when people like you, they will start the conversation asking you what you do. If they're interested, they'll buy or sign up without a question. If not, then move on.
A fan page on the other hand is for business. Provide value to your target market. Provide solutions to their problems. Engage them in conversations and get them excited every now and then. It's important that you keep your fan page alive and interactive. If you don't then people will see it as a dead fan page. It would also be good to have a custom capture page installed here so you can generate leads and sell them stuff.
It would be good to be yourself in your fan page and personal profile. Just post away. Don't worry about those who will see double. Just make sure if you post now on both, give it time to post again so people won't see you as someone who spams. If you be yourself, people will be more interested in you.
As for twitter, just sync it. No prob at all. Just treat your twitter like your fan page. Provide value. Share other people's stuff and thank them for it. Retweet some material and people will do the same for you. It's all about relationships.
One thing people tend to miss is that social media is not a place to sell. It's a place to connect and network. People don't like being sold to but they like buying and they just love buying from people they know they can trust.