While these are most likely questions you should be asking a doctor, I'll give you my unprofessional opinions:
I don't think you should take both finasteride and dutasteride (Avodart) together. Take one or the other. From what I've heard, dutasteride blocks a much higher percentage of DHT production than finasteride does, so if you believe finasteride is not enough to help hair thinning problems, definitely think about taking Avodart instead.
Personally, my experience with Avodart was a bad one, but then again I had already been taking spironolactone and estradiol-17 for months when I starting using Avodart, and everyone will experience different results.
Most of the people here who admit to taking Avodart have given positive feedback for it.