1. Does your lg have a designated area for working and nothing else? It has to be exclusive and regular. otherwise, I dont think you can claim home office expenses. for all the details, you can refer to publication 587 on the IRS website.

2. they are deductible on schedule A(itemized deduction) if not reimbursed by the employer.

3. I think only mortgage insurance premiums are deductible?

From IRS website: Premiums that you pay or accrue for "qualified mortgage insurance" during 2007 in connection with home acquisition debt on your qualified home are deductible as home mortgage interest. The amount you can deduct is reduced by 10% (.10) for every $1,000 ($500 if your filing status is married filing separately) by which your adjusted gross income exceeds $100,000 ($50,000 if your filing status is married filing separately).