I would not feel safe riding through the night without a good set of lights and lots of reflectors on my bike.

Definitely get panniers or a big seat bag (like a Carradice Camper), or at least strap the backpack to the luggage carrier of your bike. Cycling any kind of distance with a pack on your back is not fun.

Switch to slick tires.

At a bare minimum, practice fixing a flat tire.

The daily mileage is certainly ambitious for an out of shape, first time tourist on marginal equipment. But what the heck, have fun.