Sue,
If I were you, I would focus on the things I CAN control, and let go of the ones that I cannot. That is easier said than done, I know. However, once you do let go of the things out of your control, you will stop alot of the roller coaster of emotions. Think that through- you cannot control your brother's quittting, opening a new shop, your father's actions of either not staying with the business, etc.

Next, I would remember that you are ONLY responsible for your own actions. Not you brother's, not your father's. Just yours. As long as you do things that put you and your family first, what other people 'feel' is their business, their responsibility.

Then, I would make sure that you are as marketable, and that you have a resume 'up to date', and an idea of what is going on in the marketplace.

Last, here is some reality- family business, or not, you are in the same position most of us are (while we might not 'fess up to it)- replacable as an employee, at the employer's beck and call, and with the risk of having the company fold at a moment's notice. You have some benefits that I bet many of us do not- dogs/pets at work, a month's severance, and the ability to know what is going on with the place. Not meant to diminish your feelings...but, instead, make you realize you are not alone in your position.

Good luck.