It's unlikely the increase in latency just for Chennai to be due to fibre link issue.
Maybe use a tool like mtr and check the continuous traceroute with latency and see if there is any major variations.
Also, check at which hop the latency jumps to 200 ish. It's most likely a routing issue where traffic is getting routed through some other country maybe.
The increase in latency due to one more NAT layer would be negligible, maybe 1-2 ms max, so switching to bridge mode wouldn't show any major differences.