The animation breaking could be due to units on the screen versus anything to do with score. I basically just sat in one place, rotating which direction I faced, while spamming both ritual and projectile, so I had a ton of enemies and ghost allies. I'd move a little bit every now and then, but I didn't have to dodge or anything because the ritual was healing me fine, so tons of units were collecting on screen. After a point, the ritual animation stopped happening and movement became just floating versus the animation triggering.
Re the intro, you could try something like telling the backstory during a tutorial, so the player is learning the lore while they learn the commands and get their first (easy) experience with the mechanics.