If you are on the deed, he can't sell or refinance without your signature. I would consult a title agent from a local company in your state and ask them to be sure. Different states have different laws.
No he cannot.
Get an attorney to send him a ceritified letter telling him you do not want to refinance the house. Be very specific and to the point...this will be your backup plan, and also something to send to the holder of the first mortgage.
Doubtful. The deed will be pulled so that the new lending institution is assured that they will have first lien position on the property. If there is any cloudiness to the title report, such as additional owners other than the person applying for a new mortgage, the lender will typically demand that either the other owners of record appear on the mortgage application or that they renounce their interest in the property. Speak to an attorney regarding any such legal issue.