Would sand help my amp?

Ventilation and heat dissipation might be compromised. If the sand had any conductive ingredients it might cause a short or worse. The sand could have corrosive ingredients. The friction might cause cosmetic damage which would compromise resale value. Could attract pets. Might be messy.
Small fireproof/sealed bags of sand carefully placed might be worth trying.

I doubt that burying your amps in sand will do anything positive and will almost certainly have long-term negative effects. If you are concerned about the housing of your amp vibrating, or responding harmonically to soundwaves, then you might try the VPI "Magic Brick", which was "invented" to address exactly these problems.

Brightstar Big Rock sand box is what you need. Yes they work for amplifiers also.

Tizzines usually has more to do with power, power cords, speaker cables, or interconnects.

For "tiziness" address line conditioning, upgrade AC cords, & cabling compatibility issues. However, distortion only at high levels is probably just simply amplifier output-clipping, where the unit is running out of gas.
Insulating an amp in any type of sand, mud, whatever material, is begging for heat related failure. Heat sinks aren't made for their appearance, they actually perform a critical function. And if tubes are in the mix then you're really asking for trouble.