Aquapoolguide

For the algae problem shock the heck out of it right before you go to close it up, this will help to keep it from getting so bad over winter.

Visit http://www.aquapoolguide.com/pool-supplies/ to learn what you need. It might cost some money but it will save you time and headache down the road. After that you can go to http://www.aquapoolguide.com/pool-chemistry/ to learn about chemistry.

You may need a new weir door, yours could be warped. depending on how low the water is yes it could matter. This is a good link, http://www.candopools.net/repairing-weir-door-skimmer-door/

IMO i would not use test strips, they are sometimes not as accurate as liquid drop test kit, which i see you said you ordered a test kit. Also check the cyanuric acid/ stabilizer, If it is low (below 80 ppm) then by raising it you will be protecting the chlorine from the sun rays.

I would say to check the spa check valve, hope this helps.