I've never owned one with a thumb. I bought my first one specifically because it was a twist since I started on bikes. I rode my buddy's 400ex as a kid and said no way to thumb.
OMF's are tits! Close second is DWT. I bought Hipers a few seasons ago and immediately sold them. Just heavy as hell. In all honesty, if you're not riding really technical stuff with low pressure, I'd reccomend the ITP Baja's. I love mine on the trail bike and they have been abused since 2010.
How do you like that aside step on there? I hate the round style. I have OEM's on my Sierra, and this Silverado has knock offs and the plastic is slick as fuck.
In all honesty, if there is a sleeve inside the areas it's been joined, it may be ok... Dunno. Looks like a -3 or maybe a touch over. Drill a small 1/16" pilot hole like a 1/2" before the weld and see. It was cheap AF.
Not sure if what we get out of the pump has the additive for winter. I picked it up with like an 1/8th of a tank and last night the temp dropped and you could hear the pump working pretty hard to move the fuel before I filled up and did additive. Guess a Fass lift pump should help.