I am pretty sure what I described is only when --log.level=DEBUG or
[log]
level = "DEBUG"
The syntax errors are weird/concerning if it says there are errors but it still seems to load the config anyway (based on you seeing them in the dashboard).
Back when I used the file provider I pointed it at a directory and put every router/service in its own file with that volume'd in to e.g. /traefik-conf. That's probably more just advice than being your problem though.