Where do you see Dennis saying "step it up"?  The only thing close to that is his comment here to 'bump it up', which is clearly referring to DRN, the Wikipedia:Dispute resolution noticeboard which is a step in the overall Wikipedia Dispute Resolution process; and it is very clear that User:BeCritical understands that Dennis is talking about the WP:DR process, because BeCritical actually refers to Arbitration, followed by Dennis mentioning WP:RFC/U and Wikipedia:Arbitration.  "Stepping it up" and/or "bumping it up" has nothing to do with a suggestion to go to more extreme behavior in an attempt to elicit a sanctionable reaction from you.  Nor do any of the other comments by Dennis even suggest such a thing be done, or has been done.  

Secondly, you were indeed at the bright-line threshold of WP:3RR with three clear reverts in 24 hours,  Had you reverted again within the next 26 minutes (yes, it's just that strict of a line), you could have been blocked without further warning, since you been warned about 3RR several times in the past - it was very generous of Dennis to warn you.  You were edit warring against multiple other editors.  And just a reminder that you don't have to cross the bright-line threshold of WP:3RR to be blocked for Edit Warrring, so be more cautions and find consensus on the talk page instead.

Dennis is a fine admin and has been nothing but helpful and nice to you, I think you should return the favor, show him some Good Faith and stop the accusations of wrongdoing on his part.   ☥