Iron 5,000 mg; copper 2500 mg; zinc 5000 mg; manganese 4000 mg. 

These are conservative estimates; for horses, it is likely you can go much higher with safety.

You are well within the safe limits; for high-iron or high-manganese hays I have often added similar amounts of copper and zinc.  It is perfectly safe, but we are not used to seeing these amounts in "regular" supplements, so it can look a little startling.

Salt can be a deal-breaker for some horses; oddly, they don't seem to mind the copper and zinc. Start with small amounts of salt; provide loose salt in a bucket as well as a block; and give her a little time.  Sometimes when horses are deficient in salt, they lose the normal salt appetite; once they get caught up they are quite keen to eat the salt.  You can try syringing in small amounts of salt as well if she really refuses to either eat loose salt or lick the salt block (it is important to have both, because horses often can't get enough salt from a block due to their smooth tongues)  There are some horses where the owners are just stuck with only a tablespoon in their meals, and either syringe the rest in or make sure there is plenty of loose salt available.

Nancy also has a fab recipe for salt cookies:

As time goes on, I promise you will become more efficient at making horse brekkys and dins; we all have our routines eventually.  :)

.......  So I'm pretty sure this is what I would have to add to her diet for a 4:1:3:3 ratio.