Germany, France, and the UK have collective military expenditures of $340 billion,

So? Germany, France and the UK have vastly bigger GDPs than the Poles do:

Germany - $5.45T
UK - $4.26T
France - $3.6T
Poland - $1.1T

Since you went with the collective number of $340B, that's against a collective GDP of $10.81T, or 9.8x what Poland is. Therefore if they were paying the same as Poland their collective expenditures should be north of $560 billion. NATO countries also game the GDP expenditure stuff by counting civilian infrastructure and pensions as a part of their spends.

Now let's do population

Germany - 83M
UK - 69M
France - 69M
Poland - 37M

So collectively they have 6x the people. That means they should have over 1.3M active duty military personnel.

I know you're trying to claim absolute numbers as your argument but that falls apart when we look at the proportions and the will to use them. I recall a US News and World Report article from the early 1980s before the wall fell and the Warsaw Pact was still a thing. It quoted a US Army officer who was stationed in West Germany. He was commenting on our NATO allies. His quote - which always stuck with me - was this:

"I'd rather have the Poles than the French".

Amen.

You're trying all kinds of dodges and weaves to get around the fact that the other NATO nations can barely field anything should the need arise.