My First AG Ready to Pitch DADY But Questions

[Wannabee]

First AG try. I researched this ad nauseam. I hope I included all relevant info. So I started with the following simple recipe:

10 lbs flaked corn
2 lbs Breiss 2-Row Crushed Malted Barley
2 tsp HT Alpha Amalyse
6 gallons water - Ph approx 4.8

While heating water, I added 5.2 Ph Stabilzer which didn't work for shit. Checked throughout mashing using brew store Ph strips
At approx 165-170 degrees added flaked maize and gently cooked until gelatinization occured.
Added NGS HT Alpha Amalyse - per instructions worked best between 150-190 degrees. Cooked a bit longer. Killed heat....
At 153 degrees, added 2lbs crushed malted Distillers Malt (2-Row)
Held heat pretty steady between 150-156 degrees for 90 minutes

No conversions using Lugol's Iodine
Brix was 17-17.5
Ph still sitting at approx 4.8 c

After 3 more hrs same results. Temp varied between 135 and 145 degrees after initial 90 minutes.

I ran out of time so I squeezed bag and transferred to fermenter. A little sparging gave me a final Brix at 16.5= SG 1.067

So non-conversion caused me a bit of stress. Maybe..........
-the Brix reading may be inaccurate due to starches being present?
-the PH of water was too low?
-temperature ranges of barley and amalyse used incorrectly? - opinions ranged all over so I stuck with averages
-there's nothing to worry about?

Thanks in advance for your opinion