I have tested in the spring that runs up top. It has about a 40ft creek as it run into pond. Levels were under 3 mg/L. Doesn’t seem like it. One up top and one listed in pic above as “Under water spring”
1 – I am sure I can do something and report back
2 & 3 – I just did Amazon thing. I thought by the amount of water being moved visually, it was plenty. Here is the link https://www.amazon.com/dp/B0DLWC1WNJ?ref=ppx_yo2ov_dt_b_fed_asin_title

I'll be back out there next weekend. I'm thinking about moving A1 towards deep end. I originally didnt because i was trying to oxygenate water as it came in by the main spring(top side one)