From what I know, padparadscha sapphire is the most expensive colour (it's like a mix of pink and orange), followed by royal blue. The other colours should actually be cheaper, I think you should be able to get a 1.5-2ct pink or yellow sapphire under $3K :)
Sorry to hear that. Family is always difficult to deal with. But tbh, I think in your case, if everything went smoothly without major disruption on that day, just let it go ba. Trying to take legal action might just open up a can of worms and lead to more stress + expenses from a long legal...
There's also Madly Gems which is quite popular. My fiance (then bf) and I went there together, but their range is quite limited (maybe our budget too low for them) and it's super ex!! Quoted us like $3-4K for tanzanites, and not even including the ring design yet.
With gemstones you also have...