-vam (this) only works if you are using, "that," as an emphatic (i.e. "Whoa! That teapot's pretty dirty."), but if you are using it to actually differentiate two choices then you should use -vetlh (that) (i.e. "That teapot's pretty dirty, but this one looks OK.")

Indeed; -{vam} works for most cases where there is only one teapot, and it's fairly close to the speaker. In other contexts, it gets more complex.

There's also the ambiguity of "pretty" to worry about:
If it really means "not very", one can add {loQ} to the beginning of the sentence.
If, by meiosis, it actually means "very", you can instead affix -{qu'} to the end of {lam}.
If the "pretty" is only there to make the sentence more casual, it remains unchanged.

Humans and their weird expressions, eh?

I don't think I have ever heard "pretty" used to mean "not very". Can you give me another example where that meaning is more clear?

I also do not know what meiosis means when applied to linguistics. Could you explain that?

Actually, perhaps "not very" is a bad description, Dictionary.com gives these definitions:

adverb
10. fairly or moderately: "Her work was pretty good."
11. quite; very: "The wind blew pretty hard."

Wiktionary gives:
1. Somewhat, fairly, quite; sometimes also (by meiosis) very.

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Meiosis is an intentional understatement, sometimes in order to add emphasis.
"That's pretty rude!" really means "That's *VERY* rude!"

Thank you. I still can't imagine a context where <loQ> at the beginning could mean any of those definitions you posted, but putting <-qu'> on the end of <lam> is definitely an option when the, "pretty," is meant to mean, "very."

Yeah, {loQ} is perhaps a bit too much on the "low" side of the scale. If anything, it'd be {tlhoS}.

I feel like <tlhoS> is even "lower" than <loQ>.

Yes, I suppose in order to make {tlhoS X} work, X needs to be slightly stronger than what you actually mean.

"It's very good." -> {tlhoS pup.} = "It's pretty much perfect."
"I speak the language well." -> {tlhoS Holvam vIjatlhlaHchu'.} = "I'm speak the language pretty much perfectly."

I wonder if the word {loQHa'} would make sense.

loQHa' and tlhoSHa' have both been suggested for meanings very similar to "pretty" here, but there was much arguing over them. I sort of like loQHa', but use it at your own risk.

Yes, I also like {loQHa'}. I think it works quite well because it seems like fairly clear that it means something more than {loQ} (maybe a fair amount, maybe a huge amount, but at least more than {loQ}), whereas with {tlhoS} it's a bit unclear if it's more or less than {tlhoS} (would it means "more than quite" or "not even close to quite"?).