Hi and welcome!
Q: I love SFQ and have been practicing 30-40 minutes a day for 2 weeks. It would be much more practical for me to break my session up into 15-20 minutes in the morning and then the evening. Although I know it's ok to do this, do I lose some benefits by splitting the session?
A: I doubt that you would lose benefits. There is only good, better and best. More is best. But you still receive benefit.
Q: The second question - every 3 to 4 minutes I'll get an intense itch on my ankle, arm, etc... that I have to scratch. How detrimental is this interruption?
A: Oh my God! Don't do that!
Just kidding
Always scratch an itch.
Q: The last question - Touching my tongue lightly to the roof of my mouth creates a buildup of saliva. I have to move my tongue to swallow every minute or two. Again, how detrimental is this interruption?
A: That's good. Saliva aids in digestion and is believed to have Qi as well. No detriment is involved.
You are doing good. Keep going! More QI!