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the lack of yard impacts him. Some of our worst times are at home because he simply has nothing to do but bother everyone around him and get into trouble...jumping on furniture to burn energy etc. We do have an attached garage so I am looking onto getting a small trampoline or something so I can send him there to jump out his energy.
Kids do benefit from exercise and having a way to get the wiggles out.

If the garage has a concrete floor, this may be a dangerous surface to land on if taking a spill from a trampoline. While every physical activity has risks (and no physical activity presents risks as well), here are some ideas which other families have used:

Indoor:
- Wii fitness exercise games.
- Stationary exercise bike. There are stands for use with a conventional bicycle.
- Cardboard boxes to make a fort and tunnel to crawl around in.
- Somersaults, learning to stand on one's head/hands (usually against a wall).
- LOL, jumping on the bed used to be a thing. Not saying it's safe in all circumstances.
- Is an active class such as gymnastics, swimming, soccer, or a martial arts a possibility?

Garage or outdoor, limited space:
- Jump rope or hopscotch only needs a small area.
- Basketball.
- Roller skates or scooter, used with helmet, elbow pads, knee pads.
- Suspending a ball from a tree limb or rafter, for batting practice. Beware, the ball can swing and hit anyone standing in the immediate area.
- Taking a walk with you, while you push baby in a stroller.
- Taking a bike ride with you.

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husband... it's tough to get him on board.
Might it help to have your husband totally in charge of DS at some time period when DH is not deployed? For example, in the immersion experience of parenting DS, DH would not watch his football game unless watching it with DS and interacting with him, DH would plan meals, coordinate activities, run errands with DS, ensure rules are followed by DS such as bed making, hand washing before/after meals, and DH would be the go-to person for question answering. DH could field complaints and supply solutions. There may be a novelty effect for a while, but DH may begin to see and hear DS' cries for help through his various behaviors.

With much at stake, helping your son may not be a totally DIY endeavor: a professional familiar with gifted may be of great help.