Independent appraiser, not jeweler. Unless you tell a jeweler that it’s a “family piece” (vs. inherited it) and ask them “what can you tell me about this”? Not “I bought this from somewhere that isn’t here and want you to say i got the best deal (they won’t, but they will probably offer to sell you something that’s “better”...)
(meaning, find someone independent—who has nothing to sell you but their knowledge)
Still LOVE the look of that ring!! So excited for you (both)!
I absolutely love that ring! I like illusion settings, and had my r-ring diamond mounted in one back in the early '90s when "vintage" style was not hot and "vintage" was still considered just some old out of style ring. I don't think that illusion mounting takes away from the diamond at all. The only thing is, the rhodium plating will wear off and to keep the look up, the mounting might need replating once in a while, or annually.
I hope you like that jeweler, because now you can use him for cleanings and whatnot. Sounds like he made a fair assessment of your ring (and didn't bash the fact that you didn't buy it from him). A G colored stone is VERY WHITE (SCORE!!!) and eye-clean graded conservatively SI1 is not out of the question. Nice that he complimented the workmanship and also had a backstory about a similar setting.
I really love the design and am so glad your lady is going to love it. You got a really nice product for a very nice price. !! Yay !!