As far as I know, the first issue about the voting data was incompetence by some low-rank campaign staff guy, who's been dismissed shortly after that story broke. Plus no real Clinton voter data was actually taken from the database, they (aka one guy from Sander's staff) just accessed the database. Which, again, is pretty incompetent but only marginally ethically reprehensible and has nothing to do with Sander's personal integrity. I actually found the DNC's reaction much more appaling.
Don't know about the Nevada stuff tbh.
And I've just watched the New Hampshire ad, to me it's pretty clear that the Telegraph and that other second paper doesn't endorse Sanders per se, I mean the large "Endorsed by" box is pretty obviously removed imo. Maybe it could've been better, but that's no scandal whatsoever.
All in all, with a huge number of people involved in your campaign, you ineviteble get some guys that try to bend the rules, or simply do not realise that what they are doing is wrong or forbidden. Clinton supporters for example pulled some very sketchy $#@! at one or two Iowa caucuses concerning vote recounts, something much more serious.
And in terms of political integrity, in terms of how steadfest and long-lasting their stance on political, social, economic issues have been, Sanders is simply miles ahead of Hillary.
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Also, that Rubio rumour really seems like pure BS.