There is a Martial Art that literally destroys both striking & grappling arts like Kickboxing, Wrestling & Jiu-Jitsu and it is called Pekiti-Tirsia. Even against Bigger, younger, stronger assailants who may be well trained in BJJ & MMA!! Pekiti-Tirsia is a completely different body of material that begins your training with weaponry to develop a unique Combat Geometry that transfers into devastating empty hands skills for close quarters battle.
Pekiti-Tirsia is not a sport art but a Tactical Combat Trade taught to Navy Seals, Recon Marines and Special Forces in multiple Nation States. IT INSTILLS THE INSTINCTIVE PERFORMANCE of Tactical Material NOT sport to END THE THREAT.
You will not be meeting bigger, younger assailants "force for force" but always out performing them with a more practical answer to the violence they are threatening. Of course there is more to understand but bottom there IS A WAY for you not only to survive over 50 but THRIVE under these circumstances.