I can imagine you are frustrated, but this, too shall pass. While maybe a second opinion is indicated, the routine for Coumadin is fairly established. I believe there's more than one person on this board who's been through this.
DH has been on Plavix for 5+ years. While it doesn't need to be monitored with quite the same attention, it does cause an annoyance with every little cut/bruise, or minor bike crash. But, eventually, you learn to deal with it.
Good luck!