When you say all the way to the top where the red thing is, if you 'mean' all the way to the top, that's too high and why you've been blowing up ETs. It should be where the two balls on that red dipstick straddle the top of the filler neck. Coolant is really only slightly visible beneath the float of the tank...coolant should be 5.5" below the top of the filler neck.
Don't know the brands Pelican sells...but therm should be a plastic housing...and wahler is OE. ET, I'm not sure who is the OE maker. WP...I have a graf pump and it's been fine.