Is Business Class worth it for 16hr flight?

Hey guys, I'm going on my first international trip from Toronto to Singapore in mid August (layover in Vancouver). I'm going with Air Canada.

Vancouver to Singapore is 16 hours and I'm considering taking the business class for this flight. However it's coming to a total of $8k (round trip)

Economy class is coming to a total of $2.5k (round trip).

I don't think I would stand 16 hours in economy class, I have back issues and claustrophobia. I know these seats can be tight and uncomfortable. I wanna be comfortable for this trip as it's my first time traveling overseas.

But spending 8k on flights is ridiculous. Not sure Air Canada business class is worth it. I do like how it has more legroom and privacy and I do wanna take it.

An I being stupid about this or should I go with business class for this trip?

I really appreciate your feedback!