I recognize the need to establish a logical order, and it is somewhat similar to the infra/supra distinction. However you are drawing false conclusions from it.
In order to choose something (or someone) it is necessary to have knowledge of that which is being chosen from. I cannot choose to have vanilla ice cream without first knowing that it's an available option. Likewise, God must first have knowledge (in this case, foreknowledge) of an individual's existence (which of course necessarily implies a prior decision to create) before He could choose that individual.
HOWEVER, you are proceeding further in stating that it is a particular aspect of the knowledge of that individual (specifically, the foreknowledge of faith at some point in that individual's life) which leads Him to choose that individual.
When you say that "it is not possible that He did not know who would believe" in the way you are presenting it completely undermines the validity of needing to establish a logical order since you are essentially insisting foreknowledge of faith must necessarily precede all other decisions by God in the logical order. That's the only way you could say that there was not a point (logically) where God did now know who would believe.
To apply your position consistently, I could say that it is not possible that He did not know that those who would believe were those whom He had chosen to bring efficaciously to faith in Christ. Thus election was according to foreseen faith which faith He sovereignly brought about.
Fru, I think you've written a very honest post.
However, here's just one thing to reflect upon that sums it up for me. In personalizing this, I would use my own name, but let me use yours.
"When did God NOT know that Fru would be a believer?"
Why do you assume that God acts in accordance with what we call logic?