Hello and welcome to EL&U!
It sounds like you are dissatisfied with the phrasing in your essay. Although you can use as, like, and so on, that change doesn't address the underlying issue.
You haven't provided any examples, so let me make one up to demonstrate what I mean:
- Paul wielded his pen as though it were a scalpel.
Used appropriately, the comparison can be an effective way to get your message across. If you find that you are relying on it too much, though, try making explicit what the comparison is trying to evoke implicitly.
Suppose the comparison between Paul's writing and the surgeon's tool was intended to highlight Paul's effectiveness at getting to the issue at hand. You can replace the comparison with a direct statement of what was intended:
- Paul's writing cuts to the heart of the matter.
So to your question seeking the best replacement for excessive instances of 'as if' and 'as though', especially given your willingness to countenance "slight change" to your sentences, I suggest that some of the implied connections be made explicit.