Since you are talking about cutting a hole in the lid for a probe with a crapy suction cup i am assuming you are using a thermostat not a rheostat... however...

I would suggest buying a heat gun.. you can get little ones for 20 bucks. It will give you a more accurate reading than the probe then just adjust the thermostat for the temp on the gun reads correctly. Dont worry about the suction cup

Yes you will need an appropriately sized hide for your animal it makes a difference. Also speaking of space a 30g is too large for a baby, but you can cheat by buying wood from a rep shop and cluttering up the enclosure really well so that the animal feels more secure. DONT go out in your yard and grab some sticks DO go buy some dense wood from a herp shop and boil the crap out of it. You can also cheat by getting some cheap sterilite from walmart and throwing it in just to take up space to make the baby feel more secure.

And as Cap says it should be on the hot side of your enclosure, though you should have a second on the cool side as well.

Speaking of placement the waterdish should also be on the cool side of the tank.

At 50% you might want to get something ( a sponge in a tupperware with holes) to put on the warm side and then cover some of the screen on top with a towel or plexiglass.

Again i agree with Cap, dont even worry about feeding until you have him in a stable environment.