Let's see what you have put together so far.
1.Here "ultimately" is a so-called "sentence adverb"; usually the longer the sentence (with many subordinate clauses) it is claimed to modify, the more nondescript its role is. Put your "ultimately" closer to what you want to modify with it. If you are not really sure where "ultimately" belongs, dispose of it altogether.
2."I myself" means "I." Kill "myself."
3."I remember crying and fleeing from... implies that you remember doing two things: crying and fleeing, possibly in this order. "I remember crying fleeing from..." is a jarring way (a gerund and a present participle clumped together) of saying "I remember crying as I was fleeing from..." and makes the reader suspect that the crying was more disagreeable than fleeing.
4."an extraterrestrial monster" tells me there were other (extraterrestrial?) monsters in your house.
5.You don't need expendable "namely."
Now we have
"I remember crying and fleeing from the extraterrestrial monster, our vacuum cleaner, ..."
...and we have a problem.
You have attracted the reader's interest, and he wants to know what you were thinking then. Instead, you are trying to wind up the whole thing. Why? Explain what was going on in your mind, or describe the monstrous vacuum cleaner. Just a few words will do.
I'll let you on a secret: you have a problem pinpointing the antecedent of "which" because your brain subconsciously doesn't want the sentence to end this way. Adding a word here or there to keep grammar happy usually leads to nowhere. If you think you have an antecedent problem, redo the sentence.