well not exactly. i think that since it comes down at an angle, any reflection would send it into the ground. additionally, the projectile doesnt have enough range to fully come back to you if you space it right. side b also doesnt beat fair. in this match, he was actually just punishing your missed fair approaches with side b. if you anticipate a side b, try a retreating aerial pk fire, or take the hit with a CC, or just shield and WD > grab. you can also use things like a held up smash or dsmash on shield to break through it, which you can mix in with pk fire if he starts to get too shield happy. looking at your movement options and some of the magnet > DJC stuff you did, it looks like you have enough control over ness to get to the point you want to be at with him. I think if you played a bit more patiently, and focused on anticipating ROBs tactics, while mixing in your approach options to keep him guessing, you would see a lot of success. Pk fire, up smash/dsmash, and even magnet approaches can help beat shielding, while fair will help deal with him if he tries to challenge you with attacks to out prioritize you. a good DJC fair approach will also look very similar to an aerial PK fire approach, and its hard to anticipate which you might come up with. use magnet stalls to further enhance your unpredictability and keep him on his toes.
i seriously think patience will help a lot. not neccesarily being patient by just standing there and waiting for him to make a move (which you did a couple times), but using your aerial options to try and cover his approach options without commiting to approach yourself.