basic structure

A) "Because of....+ so....." is impossible?
When you are using “Because of”, you have already started a sentence with a “because/so” structure, that is, a conditional sentence.
In this case the “so” is not necessary since in a conditional sentence, you can only use either “because of” or “so” , but not both.

B) "Although...., but....., therefore.........." is possible?
Normally when you use “Although”, you should not use “but”. However in the sentence structure you listed, there could be a lot of variance after the word “Although” which may change the sentence structure. If the sentence structure is changed then using a “but” in the next section of the sentence is possible.
Example :
Although he worked hard he did not pass the examination, but he did not give up and continue study, therefore at the end he became number one in his class.

Above answer is correct with detailed explanations, except...
I've read many books and found no one using "Although...., but.....," structure. Mostly, we're using "yet" after although. eg:
Although John is a slim young man, yet he is a good basketball player.