Do you have an under tank heater regulated by a thermostat? That's going to be your best option for heating a tub. Get your temps and humidity dialed in before any further handling or feeding attempts. Also don't try feeding your BP so often, it will only add to the snake's stress. If it refuses a meal try again 5-7 days later. Here are links for inexpensive heaters and thermostats.
http://www.reptilebasics.com/ultratherm-heat-pads
http://www.amazon.com/s/ref=nb_sb_ss...er%2Caps%2C462