Chris. When I started interrailing, it wasnt possible at all, to use the pass in the country of residency! the two in/out bound days are therefore a big improvement!

dependint on from where in Poland to where in France you travel, the route through Germany isnt the fastest at all! for example if you go from Krakow to Lyon, its faster to go through Austria and Switzerland. Anyways, probably you wouldnt do such a long trip without intermediate stops? use them to visit other beautiful destinations.

if you live close to a border, it might be cheaper to do your out or inbound with a seperate ticket, saver fare or 49 euro ticket or länder ticket. and then you can use one of your in/out days to cross germany from Poland to France.

Lots of possibilities. But hard to recommend you the best based on the vague information you provided.  Im sure, if you describe your route more precise, this community will give you valuable tips.

In my humble opinion Germany is actually perfectly located in the middle of Europe to make a train ride around Germany (make the circle as great as you want to) that will open your eyes. On the North you will need to swim, or for example take a ferry to Norway, or cheat with a cheap Flixbus between the Netherlands and Denmark. 

You are also lucky to reside in a country where you can travel anywhere during a month for just €45, and when I was looking into its conditions, you can even travel up to stations abroad with that ticket, such that there is no ticket needed between that silly piece of track between the last station in Germany, and the first station in the neighbouring country. 

I believe it is the limitations of it that will make your journey worthwhile. After all, you've got 2 months to do it.

I was just thinking that you might even be able to make 2 spirals around Germany, with the challenge being to not travel any same track twice. I am jealous!