The window is inside clone, so it will process the window on each grain.
But replacing it with a hanning window, yes it should be possible, It would probably require a few steps, but too tired to dive in atm.
Changing number instances on clone dynamically is not possible as far as I know. But you can approach it in a different manner. You can basically just set clone to the maximum number of voices you would like. Lets say you set it for 64 voices. and then you can do this:
This is just an example made with a subpatch, you would of course need to use the actual clone object.
What it does:
If the nr-of-grains parameter is larger than the clone/grain number, then turn on audio for this clone/grain. So if you set the first argument on clone to 64, then you have 64 grains available, but if you only set the nr-of-grains parameter to 48, only the first 48 grains will have audio turned on and only 48 grains will be played and processed. It works fine, I did it in my version, as a workaround, since I was not able to change clone arguments dynamically.