I'm not sure about Dante's strength, so I don't know if she better than him. She is pretty strong though. And I think she's faster than him? Probably. As I said last page, in the second episode Ryuko cuts a hundred tennis balls into shreds in a split-second. And she becomes much, much faster than that later on, with Satsuki being her equal for much of the series. At the time Ryuko did that, she was only using a fraction of Senketsu's power due to not accepting him properly.
Mach 55 assuming the calc made is right (skimmed, accepting just cause). Now if you're pro lightning timing, then Dante has the advantage. If not, the next speed if Ma20 will be an issue, though can quite easily see DT surpassing, especially if its Dante2 who would be much faster than his 4 speed. AKA; Urm..?
The tap is a tough one (casual attacks always are), and by memory only that explosion in the stadium comes to mind. Though judging from the leftover damage (again, memory) I'd say it's still in the Building level.
Tbh the strength/dura amps of DT is a bit much.. though he 'may' need its speed amp.
What about the first video where their attacks are cratering and ripping up the ground around them, until their final attacks create a huge vacuum of force?
Though the second video where those huge stone pillars are thrown through the walls around them by the explosion of Satsuki and crazyRyuko's attack is probably her best feat imo.