Humidity/Molting for my Tarantula

Tommorow (Thurs), will be 1 week since I last gave my Chilean Rose Hair a cricket that he didn't eat at all & I'm still suspecting that he may be getting to molt soon. Part of me wants to just place another cricket in front of my Tarantula for a few mins. just to see if he'll accept it or not, but yet again I don't want to strss him out! Also, I did place 2 pieces of plastic saran wrap over the top of the tank screen cover to see if that'll help out w/ the humidity issue I'm having, & it did seem to work out well for a while. Lately, I've been playing w/ the heating lamp light too, where I turn it low during the day & the humidity then seems to increase into low to mid 60% range & the temp lowers into the upper 60's, then when I turn up the heating lamp light, the humidity tends to drop down into the high 50% range & the temps increase into the mid-to upper 70's!

Last night, I added more of the eco earth (several 1/3 cups) & mixed it in real good w/ the other soil & esp. turning it around on the way bottom. After a while, the humidity went up into high 60 to low 60% range & the temps went up into the high to mid 70's! I know I'm being really anal about the humidity/temps, but I've read that the temps/humidity has to be at the right spot in order for the Tarantula to molt succesfully! Since this is my first T, I just don't want anything to happen or for him to die while molting.

It is kinda hard to match humidity and temp. with cooler surroundings.
For the molt the levels should be for hum.: 70%-90% and for temp.: mid 70's to low 80's.

Since your temps. are so low (most tarantulas will not do well with mid 60's - thats to cold) I would defenetly try to heat up the tank. The temp. has to stay in the 70's and should not fall below.
Is there a way to partially cover the sides of the tank to hold the temp. ?

Try blocking off the lid partialy to increase humidity. If you have room in the tank, put a wider water bowl.