Rats are much larger than mice, and a mouse hopper seems awefully small... even for a hatchling BP. Go with the size of rat that equates to the thickest part of the snake.
You really should invest in a scale, as this is a very useful tool when feeding and keeping on eye on the health of your snake. You can get a digital scale from a big-box store for around $10. For hatchlings, the rule is 10-15% of their body weight for feedings.
I would think that with a 75W bulb your ambient air temp should be ok. How are you measuring - as in, where did the 74F come from? You will want a digital thermometer for measuring probably, as dials are not accurate. You can get a temp gun if you like I have both a digital thermometer stuck to the side and a temp gun (they are a bit expensive though, mine was $36 from a reptile shop).
I have the Acu-Rite thermometer with the warm side probe and the unit on the cool side, that also measures humidity.