I think Sanders isn't going to outright endorse Clinton (at least not for a while) because there wouldn't be much point to it.
He's already alienated a lot of his Senate colleagues by continuing to campaign against her once it became unlikely in the extreme that he would win (certainly after Pennsylvania). Endorsing her now probably wouldn't do much to repair those relationships, plus they'll all still know he's pissed at them for endorsing Clinton en masse early (or, in some cases, keeping mum).
It wouldn't do all that much to win his voters over to her (especially not the Bernie-or-bust types), and he knows it. He said as much in a town hall: his voters won't vote for her just because he tells them to; they'll vote for her or not based on the policies they think she'll pursue in office. Mind you, I'd be shocked if he endorsed anyone else (and he won't run on the Green ticket however many overtures Stein makes in his direction, and I think she's said outright that she'd step aside for him), and the vast majority of his voters are going to vote for Clinton anyway, but the ones who are really leery of Clinton won't vote for her just because he endorses her, and would look at other options. They may end up voting for Clinton anyway, if for no other reason than that whatever her real or perceived faults, she's not a racist, sexist, fascist, incompetent, unqualified monster, but it won't be automatic, and they'll probably be holding their noses as they cast their votes.
Also, I don't think he'll explicitly attack Clinton over the next month, because now that the contests are over, he doesn't even have the "I want to get as many delegates as I can" excuse. What he is likely to do is continue to speak to his supporters (he's still drawing big crowds) and espouse his policies, probably combined with attacks on Trump. There will be an implicit threat in this, though: don't shift away from these policies or you'll lose even more of my supporters.
If he does attack anyone but Trump or other Republicans, it'd be the Democratic Party as a whole, for doing things like taking money from corporations and (as he would see and put it) ignoring the issues that matter to poor people and young people. He may also continue to push for reform of the party's Presidential nomination contests, arguing for such things as eliminating superdelegates (or at least making them obliged to vote in proportion to their state's at-large vote), ensuring that states have sufficient polling places, and moving to open (or maybe semi-open) contests. (I'd be impressed if he made the case for largely eliminating caucuses--I say largely because there's no way Iowa would switch to a primary--considering how well he tended to do in them, but he might make it on the basis that caucuses depress voter turnout.)
As for giving money to or raising money for down-ticket candidates, I can understand why he didn't, and why he's also refusing to release his donor list to the Democratic Party--it goes back to what I noted above about his being pissed off at them for so heavily endorsing Clinton. But he also knows that there are lots of Democrats who don't agree with many of his policies, and when it comes to getting his policies through, he has about as much use for them as he does for Republicans. (I recall someone noting that back when the Clintons were trying to get health care reform through Congress, they weren't dealing just with Republican opposition, but also with the likes of Richard Shelby in their own party.) Sanders isn't going to be inclined to galvanize support for people who he thinks won't support him, and for the time being he's drawn a hard line on that.
