Bryan, since you don't appear to have any other items to manage (i.e. waterfall, spa, etc) that require a larger pump, a 1 HP should be fine - if it works. The key thing to know is if it's a one or two-speed. A one speed will use excessive power, while a 2-speed provides considerable savings. The fact that your pump turns-on simply by a light switch makes me think it's a one-speed, but you can confirm. So that will probably a bigger consideration as you move forward. As for the filter.... well ... much like the pump itself, you may not know until you crank it all up. I suspect one issue (if the pump works) is to perform a backwash and see how the filter responds. Of course you can disassemble it first (carefully) if you're familiar with the process as to be cautious about the laterals and fittings. At some point you'll find-out real quick if the corrosion caused by improperly storing acid nearby has done too much damage.
Let us know. If you end-up requiring a new set-up, TFP can guide you to a few very good products on the market that are not only reliable and efficient, but should also be the best value for your money. Good luck.