Still loving my V10 after 2 months of owning it and using it with headphones every single day so far since I got it. It sounds great with every headphone and IEM I have and has more than enough power for them all.
Why replace the headband? If it is still in good condition just chop the bumps off and stick a piece of adhesive backed felt over where the bumps have been cut off. Cutting the bumps off with a razor knife is actually very very easy.
OTG should work, havent tested myself.
Tidal has always worked eith the hifi dac. Spotify and pretty much all other music apps can work now as well, there is an app on the market that tricks the hifi dac into coming on with all music apps as far as i know.