no personal experience, but a suggestion if you can, to try to find the elevation gain you had on a given day on your overly ambitious daily expected mileage trip last year, to hopefully have a reference of what you recall how X ft of climbing per day felt like--so you can conservatively judge a more reasonable daily distance for this trip, taking into account some climbing.
I think in meters, so I know that for a given rough estimate of climbing that google maps or whatever can sort of calculate for a days ride, it gives me a reasonable idea of how hard a day will be , as well as being realistic of a reasonable distance I can do in kilometers.
and as you know now, headwinds can be a real bugger and so leave some leeway for this.
oh, and try taking less stuff this time. Like when this came up last time, taking off 5 or 10lbs off what you had (I seem to remember you never weighed all your stuff) can make a real feelable difference.
good luck getting a feel for elevation gain vs comfortable distance.
ulimately the only way to learn is to do some loaded rides as test days where a google maps route can give you a pretty good idea of gain, and see how you feel, and go from there.
good luck with this and especially the virus situation in your country, and all the side effects of store availability etc