x2 what OGM said....I wouldn't mess with nutrition by mixing it with anything else. Oats (or oatmeal) is hard for chickens to digest. Experiment with mixing the crumbles with water...eventually you will find the perfect ratio to end up with a thick gruel. If you mix in just a tad too much water, mix it well and wait 5-10 minutes, it will soak up more of the water. At that point it might be too dry and you then add just a little bit more water and wait a few more minutes. Keep doing this until it's a good thick consistency. Measure the amount of water you end up using and you should then know how much water to use in the future.
Once you know the ratio of water to feed, you could also just mix up the next day's meals the night before and keep it at room temp. It will be a mini-ferment...it will make some of the nutrients in the feed more available. This might be easier for you than the whole extended fermented feed process.
I hope your cross-beak fares well. After a year, we realized ours was very slowly dying from starvation and mercy was the kindest thing to do for her at that point. We tried different things to keep her fed, but we were not down for tube-feeding, as it didn't seem like a normal life for chicken to have to live through.
Last thing, go easy on the flax seeds, too much can cause eggs to taste fishy. I don't recall the recommended ratios, but it should be easy to search for on BYC.