Should I add a comma before "and therefore"?"

My gut is telling me not to add a comma in this particular instance.

"I know nothing about economics at all and therefore I should most likely keep my mouth shut, but I can't help it not to mention this observation I have made."

It's a conversation with a friend, but we keep it on semi-formal level.

I know that "and therefore" can be set off like this: "bla bla bla; and therefore, blabla" or "blabla bla, and, therefore, ballablabla" or "blabla bla and, therefore, blabla"

But in this instance my inner voice wants a fast flow. The most important sentence in my delivery is " I can't help it not to mention this observation I have made."

Thanks everyone.