Great post. Just to add a couple of comments, you always trade off long calls vs buying stocks on margins, trading off theta decay..., vs margin interest carrying cost. It is also not that obvious trading expiry time vs premium. In my simulations, longer dated options had inferior return than shorter dated options. There seemed to be a sweet spot that were different with different underlying. MM are getting smarter, IV for long dated options nowadays for individual equities often are higher at longer expiry making long dated options more expensive.
Granted, I don't know squat about futures but how does buying index futures facilitate the OP's goal of reducing his concentration risk in a few stocks and transitioning into diversified ETFs? It's true that options USUALLY carry additional costs but it's not ALWAYS. A no cost collar offers profit potential while laying off a large part of the risk. And when there are costs, the big picture is that laying off that risk may make option those costs acceptable.
I can't source it but I agree with you that long dated options more expensive now. When LEAPs were introduced nearly 30 years ago, they were far more attractive for diagonal spreads. It took fewer months of writing to recover the time premium paid for the LEAP.