Oh, little pumpkins!
The food question is a very good one. I think you are on the right track. At the same time, there is a lack of good information out there, in my opinion. Some folks think buying the pre made stuff is the only way to go. Others like to make their own. Joybilee Farm has posted their recipe for non-GMO livestock feed. And Mother Earth News has published one or two good articles on raising food for your flock. Also, Carol Deppe has written a book, "The Resilient Gardener," in which she writes about what she feeds her Anconas. and, Harvey Ussery has published a book on "The Small Scale Poultry Flock."
Storey's Guide to Raising Ducks, first edition, had a little appendix on feed recipes, but it is the kind of list one hands a commercial feed company.
Countryside Organic makes a couple of good layer feeds - you might look at what is in there for some ideas.
I am wondering if some kelp might be a good idea - not sure of the proportion but I know you do not want to overdo it. Non GMO wheat may also be a good idea, and just a little flaxseed meal. Buckwheat's got some good nutrients in it. So do millet and amaranth. In fact, I think amaranth is pretty good quality protein.
Another thought is - it is important for the ratios to be right. If I recall correctly, Storey's Guide states that the calcium to phosphorus ratio needs to be right, as well as the right (small) amount of salt...
Hope some of these resources give you all the information you need. I think it can be done - I have chosen for now to go with boughten feed until I can get ahold of more of the main ingredients for a home-mixed feed here.