If you mean his jumping d+HP, that’s extremely risky. You get that move blocked and unless it gets blocked from absolute max range… (a lot of times even if you hit them with it) you will die. Don’t use that move when you jump in unless it’s going to win the match for you. The majority of the time it won’t.
Also, getting caught by jump in SA1 is not that easy. Your friends should already be trying to AA you before you even get a chance to jump in. Basically all they have to do is watch for a jump in attack, and if they don’t see one just do a backwards j.HK to get away from the super. Even when you activate the super they still can jump out of it even after the super freeze. You have to catch them making a big mistake like dashing in towards you or recovering from or starting up an attack. If they’re just standing still when you input the super they can jump and escape.
Best thing to do against shotos is stay on the ground any ways. I would only jump in at them after having them grounded or if the match is already in your favor (so they’ll be more reluctant to try and AA you). Stick to keeping them outside with s.MK and c.MP and if you are going to jump in, try to mix it up. Like, try to charge down while you’re jumping towards them and then as you come down, hit them with a c.LK and you should have enough time to hit up+LK/MK and do a stomp. The LK stomp will come in front of them and force them to block regularly and the MK one will cross them up, forcing them to block/parry in the opposite direction.
Since the opponent probably won’t be expecting a low attack as you come down (seeing Alex can’t really verify anything after any low attacks), you’ll more than likely end up hitting them with the c.LK before you even go for the stomp. If you know how to charge partition you can do stuff like whiff s.MP x 2/3 (hold down inbetween each MP), jump towards the opponent with an empty jump and hold down as you are jumping towards them, then immediately hit up+K upon landing to immediately stomp on them. You can also tack on a c.LK or s.MK before doing so if you think they might try to jump away.