Okay, you may be able to close the gap a bit for the Greeks, but it doesn't affect the early-mid 1st millennium BC date for the Celtic sound shift and since you're saying Greek is away from the mainstream, the Celtic date should be more relevant to the rest (Ligurian, Osco-Umbrian and presumably Lusitanian) Also, remember that prior to 2000BC for the break-up of PIE is the most extreme late date possible with the late dates for Kültepe Hittite and Armenian urheimat theory and all of that. Take any other theory, or even earlier dates for Hittite, and Lusitanian has to stay weird for another 500-4000 years (leaving aside raving bonkers Palaeolithic Continuity theory)

Latin doesn't have labialisation: ΄ιππος = equus.