Newbie here looking for advice from experienced ratters

My husband is a coeliac and we have recently taken on three fab little bucks. They've been on Supreme Science Selective with a bit of Mix7 from RatRations thrown in once in a while to keep life interesting, but it is looking increasingly likely that I'm going to have to formulate a custom rat food that is both perfect for ratties and also gluten free, because my coeliac is starting to show symptoms of low dose, repeated gluten exposure and the rats' food is the only gluten source allowed in the house, so...
I'm looking at recreating RR Mix7 for them without the gluten-containing ingredients - I've been in touch with RatRations, who advise this approach, too. I've so far looked into the Protein, Fat and Fibre content of each of the (30+!!!) ingredients in Mix7 and worked out the ratio to mix them all to match the supreme science food on protein % and fat % (will be slightly higher fibre but I guess that's ok). [Note: will share spreadsheet if anyone *asks* but is a bit dull! I guess someone might find my list of nutrient compositions of rat food ingredients useful one day].
I'm also looking at adding a bit of gf dog kibble to the blend, because it contains loads of added vitamins and minerals (inc copper, calcium and D3), but can't use too much as it contributes a lot of protein and fat (I think it's suitable at about 5-10% of their food, but not more). Similarly, I'm thinking of including RatRations insectivorous feast at about 3% and a little kelp and spirulina powder.
I'm obviously concerned about making sure they get enough calcium and D3, but also copper since barley is good for copper and they will have to go without barley. I'm going to go through nutritional data for all the gf ingredients in Mix7 and replacements I'm planning to use, to check they will also be getting enough Vitamin A, zinc, manganese and selenium, as the SupremeScience packet tells me how much of each of these are in their current food.
Questions!
- Are there any other nutrients that you know of, that I should worry about?
- If I use things like kelp and spirulina powders that are rich in many different trace nutrients, do I need to be careful that they don't have too much of any nutrient? Any particular risks?
- A vet friend suggests nutrobal as a supplement, but it's marketed for reptiles - anyone use it?
Thanks - sorry for the long and involved post!