Definitely look for 2 one-ways instead of return.
Positioning flights out of America can do wonders for availability.
FlightConnections gives a reasonable overview.

FlyingBlue minimum rate is 60.000 for anything America-Europe (even if there are layovers)
Should be doable to book in Business straight away.
Houston/chicago/iad/toronto etc.

I agree with the rest that booking a ticket to eg AMS/London/Germany/Nordics/Anywhere in Europe will make life a lot easier and intra Europe flights can be found for as little as 12k or less. If you are brave you could even book a self-connect, e.g Den London - Lon Paris and through check luggage so you don’t have to think about it.

interestingly, I just saw DEN Paris London Gatwick for 120k (base rate). If you call in, they should be able to make this into a free stopover with as many nights as you want (max is a year or so) with Air France. Something like that would make by far the most sense. Main problem is to find an agent who knows how to do this, which is notoriously difficult. I.e at least best to call when FlyingBlue itself can assist you and read the wiki on the FlyingBlue thread/their own website.

Alternatively, I have found that it can be cheaper to buy for example Air Canada miles during a promo and redeem those rather than paying for a ticket outright. Should be able to spend those also on the Lufthansa (old business means sitting together in a 2-2), Turkish and ofc Air Canada