100 Ohm sounds wrong, and 3 Watt resistor getting warm is definitely wrong.
What have you actually hooked together? Schematic!
A 100 Ohm resistor in series in the line between MCLR pin and programming connector may be O.K.
When the programmer tool is disconnected, it will be open-ended anyway.
The MCLR pin should be pulled up to Vdd power line by a 10 kOhm resistor.
Some PIC devices have internal weak pull-up that may be used instead of external pull-up resistor.
If there is a Reset switch, and or a Capacitor connected to the switch, some datasheets show such circuits,
then there should also be a resistor with value between 470 Ohm and 1 kOhm,
between switch/capacitor connection, and MCLR pin.
This serve 2 purposes:
1: Preventing any bouncing current from switch and capacitor from causing undershoot voltage on MCLR pin.
2: Signal isolation when Programmer tool drive the MCLR pin for Reset or High voltage programming.
If there is Reset button, there should still be 10kOhm pull-up resistor from switch to Vdd supply.
These are all my opinions,