Rusted metal pole in sleeve
Eighteen inches of the post penetrating into the sleeve with rust most likely to be along most of the internal overlap will be next to impossible to get apart. One of the most helpful techniques for freeing rusted parts is heating the outer part so that it expands to loosen the joint - but that technique is not possible in this situation.

I suggest that you will likely have to break or cut out the concrete around the sleeve in order to get the whole thing removed all at once. This effort could be really a lot of work if the sleeve had been installed into its hole with concrete poured around it. 

Too bad to hear that your jack is breaking. If there were a way to apply the load on the jack close to the body of the jack as opposed to way at the tip would be way better. If the casting of the jack is actually broken or cracked you should remove the unit from service so that you do not try to reuse the jack at a future time and have a safety compromise.