I've grown flax, but I was waiting for a more "professional" flax grower to respond.   can't tell you much except it doesn't do well against weed pressure.  I kinda forget my seeding rate but I used the rate albert lea seedhouse recommended.    I grew a couple acres for a few years alongside of my oats.   I planted it and harvested it at the same time I did the oats.   we fed the flax seed to small to mid weight calves in the cold months.  kinda thought it gave them longer hair and it really made their coat shine.  the straw we used for bedding for pigs, they really liked it, and I actually thought that it helped keep respiratory problems down.     we used it as bedding for the cattle, but had two calves bloat in the time frame we used it, don't know if it was coincidence or not, but we discontinued that practice.

if nothing else it's really pretty when it's blooming, it blooms first thing in the morning and it looks like a river of water.