Another possibility is a jealous rival. Maybe there's someone who is jealous of Gohan's power or his relationship with certain characters. This rival could do things to annoy Gohan and push him to the edge of his temper.
One possible reason could be that he's a Greaser. The Socs might see him as an easy target just because of the group he belongs to. They might want to show their dominance over the Greasers.
One way is through detailed descriptions. For example, describe the look in the eyes of the attackers, how their muscles tense before they make a move. Another way is by using short, choppy sentences to mimic the quickening of Ponyboy's heartbeat. Also, having the surroundings play a role, like a dark alley with no way out can really build the tension.
One interesting plot twist could be that Gohan discovers a new power right before the wedding that he has to quickly learn to control. It might put a strain on their relationship as he has to spend time away from Videl to master it.
It's very likely he is not alive. Jumping from 9 stories is a very long fall and the impact would be extremely severe. However, there could be some very rare cases where he might survive if he landed on something that could cushion the fall, like a large pile of soft materials. But generally speaking, the odds are against survival.
In this fanfiction, Gohan might learn valuable life lessons from Grandpa Gohan. Maybe Grandpa Gohan would teach Gohan some old - fashioned martial arts techniques that have been forgotten over time.
In such a fanfiction, perhaps future Gohan could warn present - day Gohan about upcoming threats that he has faced in his own timeline. He might share his experiences and knowledge, which could make present Gohan a stronger fighter and a wiser person.
Piccolo might also be a savior. He has a soft spot for Gohan since they trained together. He could use his strategic mind and powerful attacks to outwit Raditz and rescue Gohan. Maybe he teams up with Goku for an even more epic rescue mission.