You could leave your assets in trust for your son and, if it has the proper language, such assets, while in the trust, would not be taken by your son's spouse. Another option is to form an entity (such as a LLC), transfer certain assets into the LLC and put that into the trust. Under state law ownership in LLCs cannot be "taken." You should seek the advice of an estate planning attorney in your area.
This type of probate is call an "intestate probate". Each state has different rules about who can request a probate be initiated and be nominated as personal representative. If an individual does not initiate a probate, then a creditor may. The bank is secured so it will get its assets without a initiating a probate. I see little reason why someone would initiate a probate under these circumstances.
You should find a law firm such as ours with tax, business, and intellectual property attorneys. Those firms without all three won't be able to provide adequate advice. Feel free to contact me further with questions.
You should seek the advice of a tax attorney in your area. The type of ownership interest you receive (:capital, profits, etc.) will dictate whether it is taxed upon receipt. In addition it affects how you are taxed when (or if) the company is sold. This is not something you can just pick up at a local bookstore.
Let's keep this simple, you are not required to update your Will merely because you move to a new state. If the move was because of a change in circumstances (divorce, new high paying job, etc.) then you might want to update it.
Executors are allowed a reasonable fee for their services. Executors inventory the assets of the estate and place a value upon them. Value is determined by the type of asset. Sometimes its is based by appraisal (real estate), sometimes it's based upon sales price. In any case, an "assets" value is determined based upon what a willing buyer would pay a willing seller for the assets (note a sweetheart price you would sell to a family member or a friend).
You will need to check your state's law. But your spouse may have a claim if after marriage the couples income was used to pay or maintain the house. Also, your spouse may have a "spousal election" whereby they can elect against what the receive in your will. Best advice is to see a lawyer in your state who can address your situation.
The cost depends on many factors including, the state and city in which you live, the size of your estate, the desired estate plan (i.e. outright to beneficiaries, in trust, tax planning). You should contact an estate planning attorney in your area who will better be able to advise you on the cost.