Were there any business class seats available for redemption when you made the booking?

I'm trying to determine whether you already had/forewent the chance to redeem directly into J using your miles - i.e. if the idea to try for J was not part of the original plan and is only a recent idea.

The best way to use miles to travel in J is to redeem outright into the J cabin. By redeeming into Y, you've now restricted yourself to those 2 particular flights and are now completely reliant on a seat becoming available for mileage upgrade on 2 particular flights, and remaining available even after OLCI has commenced. With current flight loads, that's a rather tall order. If there are available J seats on the AF flight between IAH and CDG on the day you're taking your KLM flight to AMS from IAH, that won't help you, because you're stuck with the flight you initially selected. And if there are available J seats on the KLM flight from AMS to IAH on the day you're taking your AF flight from CDG to IAH, again that won't help you - you're tied to that specific AF flight. Rather than obtaining Y tickets on 2 particular flights, it might have been better to exhibit greater flexibility, and already scour various routes on various dates in order to find flights that had a J seat available for miles bookings at a price you were happy to pay.

And even if you get lucky and eventually you do get to upgrade on one/either of these flights, by doing it in so many steps - first obtaining a Y ticket, then upgrading (potentially in multiple steps, via Premium Economy, based on your most recent post) - you've made the process far more complicated, and expensive, than it otherwise needed to be. If there was J availability on these flights and you didn't like the price at the time you made the booking - you're also probably not going to like the price quoted to upgrade, if it becomes possible.

Again, the chances for you to upgrade using miles are tiny. Even if it's possible, it won't be possible until 24 hours before departure - and nobody, in that timeframe, is probably going to want to deal with your request if you don't even have any miles in your account. And even if the mileage transfer in from your card partners is "instantaneous", there is still the risk that someone else will nab the upgrade that you thought was going to be yours; you're not going to be the only one looking to upgrade themselves.

I would, however, not recommend transferring miles over on "spec". For one thing - you have no idea how many miles would be required. For a second thing, once a transfer is made, that's it - it cannot be reversed.