Hi and welcome to the Chiari forum.
Many of us may have residual effects of the chiari and surgery, and if the floaters when u turn r the worst u have, that is not too bad.
The vertigo, is something else, it is possible that something else is going on, and warrants at least a NL visit.
It sounds like u did well post op until now, and that is great!!
I have not had Chiari surgery yet, but I had an extensive laminectomy in 2000. Whenever I look down & to the right(like shaving my armpit), there are sparkly lights, and I have to wait for them to go away. Apparently its a bulging disk. (That's as opposed to floaters that near sighted people are prone to.) Is this what you mean?