Re: Saftey of Old fuse box/electric/wires
First if it is knob and tube wiring it should not be covered by insulation. It requires free air flow to dissipate heat and the insulation on the old wiring drys and get brittle with age and can fall off if disturbed. As far as I know there is not yet a national requirement to replace K&T wiring although some insurance companies will decline insuring homes with K&T wiring. K&T wiring is still in use in millions of homes.
Heat is usually caused by excessive current draw above the rated capacity of the system. When the wiring was installed it was most likely sized for lighting and few electrical appliances, often times it's all 14 gauge wire rated at 15 amps. To often I have seen higher rated fuses, for example 30 amp fuses in place of 15 amp fuses, installed as appliances where added. This is an unsafe practice. It is very important to size the fuse to the wiring not the load
The fact that the system uses screw in fuses rather than breakers is insignificant as both accomplish the same thing.
Sparks when plugging and unplugging appliances can be caused by loose wiring on the outlets or plugging and unplugging appliances while the are on. You should always make sure an appliance if turned off when plugging or unplugging them.
I hope this gives you some of the information you want.
Be sure you live your life, because you are a long time dead.-Scottish Proverb