If you attempt to re-tighten it then wash with oil
first, cooking oil
will do, to get all water
Don't run with it slacker than normal, count turns carefully as you release, wind
it tightish, and re-tighten to get the same tension in it.
Loads on the forestay are at their worst working into wind and swell. sailing downwind should be fine, just take enough fuel
and pre-plan a point of no-return if the winds turn against you. Adding low throttle running to storm reefed DOWNWIND sailing will reduce your passage
. Pick the days, get the best forecast
Plan be is to fly bits out and replace. Strip out the old one, measure, cut off the old swages and send to supplier so you get exactly the right replacement. First time. And find just the right spanners for fitting the replacement before you post the old ones.
Order seizing wire with the new forestay!
Good luck. It's horrible not knowing your rig is safe.