Only backshifting, not subjunctive
Reduce it to its most straightforward word order, and the answer will become clear:
- I realized that active contemplation would be needed if I ?were to find any closure.
The thing is, I’m not sure this should be a were there, which is why I’ve marked it with a ? character of dubious grammaticality. I think it’s a backshifted real case, not a hypothetical one at all!
Here's the original, which as you see is all completely real:
- If I am to find any closure, active contemplation will be needed.
When you prefix that with I realize that in the present tense, you leave both of the other two existing verbs in the present tense that you found them in in the first place:
- I realize that if I am to find any closure, active contemplation will be needed.
Notice again those three bold verbs are all in the present tense.
Now to place the whole sentence into the narrative past, you merely swap each of the three tensed verbs from their present tense to their respective past tense:
- I realized that if I was to find any closure, active contemplation would be needed.
Since there is no hypothetical case here, you cannot use the “unreal” inflection of were, the one descended from the old past subjunctive. Since there is no subjunctive, you also cannot use “subjunctive inversion” of starting with a verb in the subjunctive and skipping the if word altogether.
- I realized that, ✻was I to find any closure, active contemplation would be needed.
That has the ✻ mark of ungrammaticality because you cannot use inversion on a subjunctive conditional when there is no subjunctive conditional in the first place. That’s a real case so no inversion is permitted!
This is valid, though:
- I realized that active contemplation would be needed if I was to find any closure.
But I don’t much care for it.