Electric shock through laptop case and LEDs stay dim but on when switch is off
The tingling is lethal. What saved you was high resistance on the rest of the circuit back to source.  This needs to be fixed ASAP.  

It might be a leaking, faulty appliance.  Plug the appliance into a RCD protected outlet and next time it shocks you, it will instantly trip.  Into the trash the appliance goes.  If it's a PC, the problem is the power supply or power brick.  

I wouldn't worry about the external RCD tester not tripping, that is the normal/correct behavior if the circuit does not have a wired ground. An RCD protected circuit doesn't really need a ground to protect you, just equipment.

Give your grounding system a very thorough once-over

It seems like you are doing everything right and still getting shocks, so the first place I go in that case is the grounding system.  It has 3 parts: 


the grounding electrode system from the panel  to the actual earth. This consists of a fairly hefty ground wire from the panel's ground bar/bus/case to ground rods, Ufer or water pipe connection into the soil.  We Americans are fond of two ground rods.  
The neutral-ground bond, which connects the ground bus inside the panel to the neutral bus also inside the panel.  In America this is often done whimsically, by just landing all the neutrals and grounds on the same busbar. But whatever.   It's more useful to have a distinct neutral-ground bond that you can put a clamp meter around. 
the equipment safety grounds, which are the "third" ground wires from the panel's ground bus to all your sockets and equipment. 


Search all of those, most especially the first two.