Can I still get my tax refund about $4000 back If I claim it right now. Will I get sued because I did not claim the tax refund?

You are still within the time frame for filing your return.

Will the IRS keep my tax refund if my spouse did not pay the back tax amount?

Probably need more facts to answer this fully but have you considered innocent spouse relief.

What does "cooperation" entail? What are my risks?

It most likely means that you will have to sign some documents for the buyer. But to make sure you are protected hire an attorney to assist you.

Can a tenant in common unilaterally transfer or surrender his/her interest to other co-tenants by quit claim deed?

Generally you can do this. But, it may be considered a gift subject to the federal gift tax.

This sounds reasonable. Sit down with a lawyer/CPA to make sure you do this in a way to avoid the gift tax.

Is it enough to file the 1120 form in order to be taxed as c-corp?

Yes you need to file form 8832 to elect corporate status. Talk to a tax lawyer or CPA to make sure this made sense.

What is the most tax-efficient way to transfer ownership in a privately-held C-corp to my family, to avoid taxation upon death?

This question has both corporate and tax questions. On the corporate side you need to review the shareholder agreement on transfers. On the tax...

There are a labor of facts that need to be reviewed. With your mom it sounds like she needs to sit down with an attorney to get a health care proxy...

How can we avoid spending $20k to relocate our driveway to match the legal easement description?

First get your own survey done. Also check with a local lawyer about your rights. You may have an adverse possession claim.

Can I be considered the owner and avoid capital gains after 2 years living in the home if my name is only on the deed?

If you are on title and otherwise qualify for the gain exclusion you should be good to take the exclusion.