A bit late to reply but I try and not visit these forums much, overall it seems to make my own issues mush worse rather than support them in a helpful way. at least this is how I'm feeling at the moment, which, like anything else in life, can and will change.
I'm in my "having a break" period as such from these types of places, just my thoughts.
So if I don't turn up here you will need to understand that
Reading what you write suggests that much of what you know so far supports the need to try dietary changes as suggested with the FODMAP focus. There are apps for your phone as well as books etc for that.
If you need a colonoscopy then that will appease any anxieties you might have about that procedure, which is relatively simple. The blood for me was due to haemorrhoids bleeding, which were banded during the exam.
You will be fine, try and work with your partner as well and I wish you all the best with that.
Take care and try your very best to remain calm, and do NOT overread things, often Google is not your friend.
All the best