That doesn't matter (or actually it makes the problem I explained more obvious). The script validation and the gas spend confirmation must be atomic, which means they must be confirmed in the same partition, else validation can not be partitioned per the logic I already explained.
They will be - the gas is paid inside the same transaction which invokes the script?
edit: but, of course that does invoke the horror of double spends - since partitions are necessarily separate and unaware of each other, I can spend the same gas in multiple partitions at the same time.