What's reasonable compensation to demand for a broken business class seat?

I recently flew Manchester (UK) to Delhi (India) overnight with a stopover in Abu Dhabi with Etihad in business class. The seat on the second leg of my outward journey Abu Dhabi - Delhi EY218 on 18th Nov was broken and could not adjust.

Given the timing of the flight this was quite annoying, I spent about 30 minutes standing whilst they tried to fix it and there were no other seats available.

I've requested compensation noting specifically that I'm not a frequent traveller and points ant really mean anything to me.

7 weeks later and 3 chasers they have offered me 10K points or a 100 USD voucher on my next flight. Besides the fact the both are pretty much useless to me, I don't think this is a fair offer.

A similar flight - in the next 3 months e.g. Mis currently priced at £99 in economy vs £685 in business class - I think this should be the benchmark of compensation. £586. They have refused to budge.

What d you think is fair and any suggestions on how I can take this forward?

thanks