I weigh 72kg, and my maximum is 5 times that, so 360mg of non-heme iron per day. It is best to split iron intake into multiple doses, 50-200mg each time.
Ferrex is Polysaccharide Iron and is generally well tolerated by most people. I personally have no issues with it. But there are lots of kinds of iron to try!
Yes there are a lot of options. Here's a table that might help. (Click on Table 1)
Since you're also in the US I'll share what I take: Ferrex 150 Polysaccharide Iron Capsules which you can find cheaply on Amazon or ask your local pharmacist if they can order it in.
The heme iron I've tried: Three Arrows (way more expensive but nice like I said to not have to worry about absorption as much). There are other brands too. Make sure you read the dosage for that on the bottle, heme is a little different.
Neither heme nor non-heme are "better" than the other. It all depends on the specific person. Honestly, non-heme is cheaper so you might want to start there. As long as you can tolerate the high doses and your numbers are rising, you might not ever need to take heme. Heme is from meat products so some raise objections to that.