Try and use as an event the following:
"A unit Starts the effect of an ability"
And also move your second and third "If (All Conditions are True)..." in the "Action" section, not the "Else" sections.
May as well replace the waits with a different trigger, that fires when the ability is cast and...
If your loading screen's width/height is larger than 800x600 or 1024x768 and is smaller than 512 - it won't display, and your case will happen: Black screen will appear as your background. Try tweaking its size and it will work.
You're adding an ability and in the same time removing that ability. You can just add the abilities you want on the alternate unit your Chemical Rage converts to.
Your normal unit has ability A and B.
Your Chemical Rage unit has ability C and D.
You can try and alter Spirit Link (Orc - Spirit Walker) in the following way:
Tweak Spirit Link's stats (see below) to your needs, afterwards make two triggers - first one, that will cast the altered Spirit Link on your unit each time it casts its "shapeshift"; second one, that will remove the...
That should show you the raw value of your "Brilliance Aura" ability.
A000 is the raw value of your custom Brilliance Aura ability. You should fill that in the descritpion, such as: