Try fios box to soundbar via HDMI, soundbar to TV via HDMI ARC. Did you try optical from fios box to soundbar? What you are describing is a VIDEO lag, not audio. The screen image is behind the audio. Try setting your TV to game mode and see if it improves. If it does there is a setting in the TV menu that is causing excessive image processing and delays the video with respect to the audio output. Also look at audio delay options in the TV menu, or sync options, and in any menu in the soundbar. I still think you should be able to get this acceptable through the delay setting in the Fios service menu.
I don't understand why it's marked as SOLVED. The "solution" reply is irrelevant, the OP is talking about an audio lag and not a video lag. There is indeed an audio lag from the Fios TV boxes when outputting in DD format. It should be solved by a firmware update or box replace by Verizon.