Could you check this over

Hi. I'm pretty sure that *weh₁i- would become *wei- in Celtic, not #wēi-. Beekes makes the exact same point about the sequence *-eh₂i- turning (generally) into *-ai- not #-āi-; *-āi- must reflect *-eh₂ei- or similar.

Ok, but ei generally becomes ē in Celtic, so does a former eh₁i also become ē or does it remain separate?

Also, the shortening of long diphthongs is because of w:Osthoff's law.

Presumably eh₁i becomes ē just like ei. Loss of laryngeals between vowels occurred early in most (all?) daughters, followed (usually) by early vowel contraction.