OK you do have hydrogen forming, that's good.
I don't know much about colored dyes, I only use black. I'll have to defer the dye questions to Mike and some of the membership who work with it allot.
A few electrical observations and questions:
The description of the anodic layer you have does sound like its too thin. Connection problems are the leading cause of this, not removing all of the native oxide from the work will do it too. The water sheeting test doesn't tell you anything about the presence of native oxide.
Good connections can be made without bolting the wire to the part. The idea is to get a liquid tight contact. The entire connection doesn't have to liquid tight, just enough to pass the required current without dropping too much voltage. In your case (12 AWG wire) that would mean at least 5% of the wire surface in REAL TIGHT contact will do. Nicking the wire where it contacts the work, so that there are small raised areas in the wire to be mashed down by the hole will help this. Its a PITA to get right at first, but you'll figure it out and it will stop being a problem. I like bolting where its possible to do because its sure fire. If you can make up some very small all aluminum C clamps (or similar) to make the connection this works well and is quick to attach.
Can you provide some details about your battery charger and dimmer? I've encountered one recently that was too small even for 3A/sq.ft.
Measure voltage and current at the load side of the current sense resistor, as shown in the battery charger /dimmer illustration in the manual. For 4.5A/sq.ft. your peak voltage will be around 11.25 V if your connections are good. Measure the voltage when its driving your setup, you need to have at least this much.
Neilfj and NeoMoses have threads here on the agitation systems they built, these threads should answer your questions.
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