It is either you want your ELCB to be more sensitive and safer for your home appliances or your want it to bee less sensitive at the expense of safety on your home appliances.

Maybe it was tripping at lover surge voltage than specified because a bit faulty not out of spec. You can buy any branded one and change if you suspected it is faulty. Any known brand should be fine. to the other one, no, it has nothing to do with fuse in fuse box.

To be honest, the ELCB is not fast enough to protect your more sensitive electronics based equipment. I woun't mind if it trips earlier