Just summitted my first speedrun! Also does anyone know how to get the
000 milliseconds instead of 00! on livesplit

I don't believe LiveSplit goes out to milliseconds.

It would be in Edit Layout > Layout settings > Timer > Timer Format , but I think you would need to download an extension - the default will let you take your choice of no miliseconds, 1 decimal or 2 decimal, but doesn't go any higher.

I know that LiveSplit internally saves milliseconds, but to show you need to export the splits files to splits.io