Julia Thank you for taking time to write such a thorough post. From Epicurean perspective, I don't think there is much material regarding time available, but I want to mention two, maybe not so obvious, sources which I find particularly interesting.
1) Sextus Empiricus "Outlines of Pyrrhonism", Book 3, 137 (I provide two translations for comparison):
QuoteEpicurus (according to Demetrius the Laconian) [defines time] as "a concurrence of concurrences, concomitant with days and nights and seasons and affections and nonaffections and motions and rests." - R.G. BURY - "OUTLINES PYRRHONISM" (1990) p. 235
Epicurus, according to Demetrius the Laconian, [defines time] as an event made up of events, accompanying days and nights, seasons, pathe and the opposite, motions and rests. - BENSON MATES - "THE SKEPTIC WAY Sextus Empiricus’s Outlines of Pyrrhonism" (1996), p. 195
2) Epicurus, On Time (PHerc. 1413/1416)
If I remember correctly, someone has already mentioned this Herculaneum scroll in the forum (sorry, I don't remember exactly where I've seen it). I don't think there's English translation of the scroll available, but there's a summary of a talk from 2022 by Alessia Lavorante in the pdf linked below (pages 7-10) where a lot of information about the scroll is provided. Definitely worth a read.
http://www.herculaneum.ox.ac.uk/sites/default/files/2022-12/HercArch_27_2022%202nd%20version_web.pdf