I have a little experience with Ike. Here are some of my thoughts.
Never let him jab you. It is so fast and annoying, it is easily my least favorite thing about fighting Ike. I'm pretty sure he can jab if you try to jab cancel a grab or an over-b. It isn't really feasible to never get jabbed, but try to limit mistakes that take you there.
Don't uptilt him when he is behind you in his shield. Instead, turn around and grab him or escape. This goes for pretty much every matchup.
Ike should never be able to recover if you force him to use up-b. A fully charged AS (FCAS?) hits him out of aether, so does a Fsmash and probably dtilt and I would even risk bair and ftilt here. BUT you should not do that since Fsmash and FCAS are soooo good at murdering him. Ike has to be a little high in damage for this to work, otherwise the knockback just sets him up to over-b to the stage. If you do it properly at the right damage, you'll probably have to hit him two or three times as he continues to try aether, but he will eventually die.
My thoughts on DDD are somewhat limited, been a few years since I fought a good DDD. This is a game of cat and mouse, you happen to be the mouse most of the time. If you get caught in a chain grab always remember a throw can't kill you. So if he just keeps grabbing you, assuming this isn't a walkoff area, you're safe. A mistake I remember making a lot is trying to mess with his timing by spot dodging after the downthrow. He caught on pretty quickly and started throwing in random dash attacks. DDD's dash attack will kill you. Jab him out or shield if you think he is going to do this. Much better to get grabbed than killed.
Don't bother using FCAS or even baby AS's when DDD is throwing those guys at you unless you are sure you know how to hit him in that move. Save FCAS in your ledge guarding game or when he is approaching and you are in free fall, come out of free fall with FCAS right in his face. I like to do this a lot. People do catch on, but if they keep approaching it'll at least give you time to land as they shield.
Fsmash can keep DDD at bay, and I bet dtilt and ftilt would also be workable. However, because of the chain grab and throwing his little ***hole minions, DDD still dominates the ground most of the time and negates AS. Learn how to maneuver around waddlewhatevers. Learn where the holes are in his defense when he throws them. With proper spacing and timing, Lucario can hit him with an AS while he throws. There's just usually another one in the way. Practice short hopping and retreating with fair, bair, nair. practice short hopping into air dodge, landing behind him with a charging AS on his shield. Practice short hopping into air dodge while DI'ing back to where you were and then Fsmash. Practice all the things.
Learn how to wall cling on FD and all the stages, it will help your recovery game immensely.
Dair is your best friend. At 2:26 you missed a grand opening to stomp on his face. always always hit with your dair when you can. It comes out super fast. However, don't use it to stall too much while recovering vs DDD. it sets you up to get bair'd. Nair is also super fast and has very little landing lag, learn to shff nair. I like to do that into jab -> dtilt or jab -> forcepalm or jab -> ftilt, and if the positioning is right, you might even try a shff nair -> grab, as our grab is awesome when people are in the air, and Lucario can recover really fast from nair. Or, after doing it so many times, jab -> wait for them to do something dumb trying to get away and punish. Think about how Marths like to up b so we can't chain grab them. Imagine predicting that and having a FCAS ready. Bait everything you think you can.
Tell your DDD friend to use over b more. That's about all I can think of right now. Sorry if it seems like I'm rambling. I am.