Will polyurethane control arm bushing give my car better handling?

If the control arm bushings are still good don't spend the money on those polys.

The average labor cost for control arm bushings replacement is more than four hundred dollars. You have already flushed way too much credit card money down the toilet trying to upgrade your ancient brick. If you did not live rent free with your parents, you would be broke.

If your old ones are worn out then yes. If not then no. KYB struts are as good as OEM but no better.