What is the ruling on my prayer if, when in doubt about omitting a pillar, I based my decision on the greater likelihood, and then, when in doubt about the number of prostrations, I based my decision on the lesser likelihood and performed the prostration of forgetfulness (sujud al-sahw)?

If doubt afflicts a worshiper, such that it occurs daily, even if only once, then he should base his action on the greater certainty and not perform what he doubted. However, if he bases it on the lesser certainty and performs what he doubted, his prayer is valid, because he abandoned the wider scope and returned to the original principle. Therefore, what was done in the first case, building upon the greater certainty, is the ruling, and what was done in the second case, building upon the lesser certainty, does not invalidate the prayer.