1) Don't smile and fake-laugh when 45 is talking over you. It's not a joke. The U.S. presidency is a serious matter and everyone should take the election seriously. Don't let him make a mockery of the debates. Stand in front of a mirror and perfect a stare that says "what the hell is this jackass doing." And have a bunch of short, understated responses ready.
The next time DT tries to talk over you, you give him that stare. Wait for him to finish. Then deliver a very mild taunt, something like "you talk over me because you don't want the people to hear what I have to say. What are you afraid of, Donald?" Don't wait for his answer, just return to whatever you were trying to say before. When he starts in again, repeat: pause, stare, mild taunt. "You know, in the sensitivity training they teach old white men like us the value of listening.
By listening we get the benefit of everyone's voices and perspectives. That can't happen when we just talk over others and drown out their voices."
Just keep doing this. Or find something else that works and do that. But make him pay. Every. damn. time.
2) Stop bringing up your sons. Nobody cares about Hunter Biden's business deals in the Ukraine except the trump crazies, so at most you're just wasting everyone else's time. And you can hit DT for calling military people suckers and losers without talking about Beau Biden. If DT brings up your sons, then hammer him for it. But when you bring them up yourself, it signals that attacks on them are fair game.
3) It's okay to admit that Bernie Sanders has some good ideas and you incorporated them into your platform. That is what you did and rightfully so. When DT attacks you for supporting things that Sanders talks about, say that: "Yeah, Bernie Sanders and I disagree on many things but he has some good ideas and I am not going to turn my back on a good idea just because it comes from one of my opponents." You could also mention how Sanders is a good person who has contributed much to his country, etc. and use it as an opportunity to explain how people with different political and economic philosophies can still come together and work for to make the country better, rather than demonizing each other and doing the trump stuff.
4) The part where you started talking about the benefits of the Green New Deal was great--then you said you don't support the Green New Deal. WTF? You need to get straight on that ASAP.
5) You keep taking personal credit for shit that happened under the Obama administration. "I fixed the economy... I created jobs... I reduced crime..." That's a bad look. You were part of that administration and deserve to share in the credit, but you should say "we," not "I." The only person who could get away with saying "I" in that context already served two terms and sure as hell wouldn't need debate coaching tips from people on Facebook.
Okay, rough first outing Joe, but two more opportunities remain. Get back to work, and kick Cheetochet's orange ass next time you take the podium.