Can omega-3 acids be effective for multiple sclerosis ?

If someone is physically and mentally fit, and has a diet rich in omega-3 acids, do they need to take dietary supplements containing omega-3 ?

How long do you advise taking omega-3 acids ? Do you have to take them all your life ?

I've been advised to take an omega-3 product for heart disease and for problems with cholesterol, skin and arthralgia. Can OM3 help with these problems as well, or just with emotional stability ? Do I have to take two different products ?

What are the possible side effects of omega-3 acids?

Can you take omega-3 capsules during pregnancy ?

If my diet contains 2 - 3g of omega-3 acids daily (for instance, 100g of mackerel = 2.5g of omega-3 acids, etc.), can I deduce from that that I've ingested 2 - 3g of a mixture of EPA and DHA ?

Could it be dangerous to ingest too much omega-3 acid (that is, eat a diet already rich in omega-3 acids, and add too much extra omega-3 as a supplement) ?

Some nutritionists recommend combining omega-3 acids with selenium. Is this a good idea ? What would be the dose ?