I can't seem to find any dictionary that has the tones written up. Does anyone know if one exists?
It is rare, it's mostly marked in academic works, the only easily available dictionary that marks them for some words I've seen - http://www.tezaurs.lv/llvv/
Or is it possible to guess the tone from something?
I don't think so
Also, does it change when the word is conjugated?
Are the tones pronounced always or only when the word is emphasized?
Also, I don't really understand the lauztā intonācija. It is described as "rising pitch followed by falling pitch with an interruption in the middle or some creakiness in the voice". I can't produce this.
I think it's a sound with a glotal stop in the middle, Latvian Wikipedia says that linguists also mostly think it's something like that
Thing is they've evolved into something else in each dialect and therefore there is no agreement which to use in standard language, except some fuzy idea that stieptā intonācija should be differentiated from nestieptā i.e. whatever else. There are some minimal pairs that differ only by these pitch accents, but mostly not knowing them just means mildly funny accent not an epic catastrophe since even the minimal pairs can be told appart by context