Re: How much anchor chain?
If I was equipping Harmonie from scratch, I'd likely go with 100m of chain, although I'd stay with the 10mm chain we have. But we bought her with 60m of chain spliced to 60m of line. So far, in cruising the East coast of the USA and the windward islands of the Caribbean, we have yet to deploy all 60m of chain.
On my old boat I had a similar setup, and there were times anchoring in Hawaiian waters I deployed all the chain--and most of the line--anchoring in almost 15m of water.
I figure I can anchor in nearly 10m of depth (@ a scope of 7) without the splice touching bottom, so shifting to all chain hasn't really been a priority. I might change my mind when our cruising ground includes deeper anchorages of the South Pacific, but on the other hand Harmonie has been around the world twice with her current setup, so it can't be too bad!
Something to consider, is that an extra 50m of 12mm chain will add almost 200kg to the bow. That's a LOT.
So... I haven't got an absolute recommendation for you, and likely haven't told you anything you haven't already thought of. It would be easy to find someone to make an absolute statement that 100m of chain is "required" and also you'll be told that what you have is fine.
From an anchoring perspective, 100m of chain would be better, from a sailing performance perspective, the extra weight in the bow is a significant downside. I don't think either choice is obviously wrong, just a matter of priorities.
Great Guana Cay, Abacos, Bahamas
(where we are always anchored in less than 3.5m of water!)