Hi. i don't know anything about the second mutation, my daughter has 2 deltaF508 mutations. I do know that while mutations play a role in how the cf symptoms present themselves, they don't mean you can determine the severity or overall outcome.
The best thing you can do is preventative care and keep him away from people who are sick.
I know, as I'm sure most here do, what it is like to wait for the worst to happen. But please try not to. My daughter is 19 months now (diagnosed at 6 days old) and has yet to have a cold. Others her age have been much sicker, but I wasted time waiting for the worst instead of just enjoying her and watching her grow. She has hit a few bumps with weight gain but has overcome those. Bumps in the road are bound to happen, but stay positive, advocate for your son and do whatever you can to help him.
If you need to talk or get advice, come to this site, private message me or ask the community. Everyone here is so helpful, they have been an amazing benefit to me and their advice has been invaluable.
Congrats on your baby! Enjoy this age!