Forget MZFW TOW limit - it is simply a nonsense. It is not a limit unless your airline, for whatever weird reason, has chosen to make it a limit.
You can add fuel until you reach one of your calculated limits for today's flight or a structural limit. Today it's 1.9T extra from LDW limited TOW. You will, of course, have a slightly greater sector burn due to the increased weight but it would be tiny. Keep it for a bit of a margin if your flight time is a bit less.