Yes, under my conspiracy theory, he would of course have "tried" to buy ammonium nitrate. Note the report says the store owner was nervous because Henrich was wearing a green vest with wires.
Obviously Henrich did that on purpose. Unless you think it is normal to wear your in-progress suicide vest with you when you go shopping for bomb parts. No, the wires were there to attract attention.
So was the downloading of islamic literature. Henrich counted on people jumping to the obvious conclusion that if he had a muslim roommate, they all must be terrorists, since all muslims are terrorists if they also attend a mosque and live in Oklahoma.
It's just speculation, but as I said -- what specific information do we have to refute MY speculation?