I saw it mentioned on another thread but it was through the wishbone to try and stop the sleeve frome siezing on the bolt. It then occurred to me that I might be able to do that to the subframe (the only times I have replaced the bushings before I have ended up replacing the bolt so im not worried about the bushing sleeve).

 

+1
Agree that drilling a small hole vertically down will not affect the subframe but I'm concerned that penetrating oil is not helping.

Also agree that grinding the middle section to cut the bolt will help.

I think you need to try a version of your very first option. Which is to drill out the bolt from both sides. I do not mean the full diameter as this risks damage to the subframe bore. But, if the bolt is 12mm diameter (I'm unsure) and you drill out to 8mm or 10mm of the core to reduce the cross sectional strength. Then this would enable micro compression of the bolt when pressing it out.

Obviously you need only go a certain depth and there is risk if you drill off-center because it gives less opportunity for concentric core reduction.

 

I'm really surprised with all the effort you have made, no movement.
Now, it's got to the point of the final countdown for that bolt. Take the necessary parts off to get the subframe out of there and take it to a shop with a BFP and some heat and you will either have it ready for all the new parts or a good used part will be required.
It has to be very frustrating with all you have tried and the time spent.