Well, he might use his powers secretly. Like, he could use his super speed to be on time for every class without even breaking a sweat. And when there's a bully in school, he could give them a little scare with his strength, but not too much to expose his true identity.
The relationship could develop out of a need for companionship. Gohan, having lost many of his friends and family in battles, is in need of someone who can understand his pain. 18, being an android with her own complex past, also longs for someone to be close to. They meet and initially just offer each other a listening ear. As they talk more, they find that they can comfort each other in ways no one else can. This emotional connection then grows into a romantic relationship, and finally, they marry as they realize they don't want to be without each other.
In the long run, they might realize that they need to change their behavior. They could start thinking about how to make it up to Chichi. Maybe they'll go and do some nice things for her, like getting her some flowers or cleaning the house really well without being asked. This would show that they've learned their lesson and are trying to be better sons.
In a crossover with the Avengers, Iron Man could be an ally. His high - tech gadgets combined with Gohan's power would be a great team. Also in the Pokémon world, Ash could be an ally. Ash's knowledge of Pokémon and Gohan's combat skills could be useful. In the Bleach universe, Ichigo could be a strong ally for Gohan, with their combined sword - fighting and energy - blasting abilities.