Hello and welcome to FF! When and where was that "Repti Day" in Norfolk? Guess I missed it
. Lija gave you some good tips; here is what I would do in your case.
Humidity and temperature - Both of these will hugely benefit from closing most of the enclosure's screen venting. I do this with aluminum foil. Depending on your fixture and top, you can either place the fixture in the uncovered 1/2 (ExoTerra or Zoo Med enclosures and similar); or if a full screen top, can do following.
Place your fixture on top of fully covered screen top, and using a marker, draw a line around it's perimeter on foil. A scissor will work well to cut the marked out hole; just make it larger by around an inch. With restricted evaporation, a couple day misting's should help keep humidity around target (70-80%). Once connected you can use the built in dimmer to adjust the heat output. If you already have a light fixture; will need to add a manual (rheostat) or automatic (thermostat) controller to it.
Temp need to go up as stated by Lija. You can't use blue or daylight type bulbs with an albino. My recommendation is to use a 60W ceramic heat emitter in a dimmer type dome like Fluker's makes. In absence of that, you can also use a red bulb 24 hours a day with no issues. If the 60W CHE is not enough to bring the enclosure to 82F during day with a couple degree drop at night; will need to supplement heat with a side attached heating pad or similar. You need to correct this ASAP since low temps will cause permanent damage to your frog's kidney and lymph hearts.
Indirect window light is more than sufficient as long as the sun does not reach the enclosure directly. Plants are a matter of decor choice as long as frog has something to feel safe. Most Pacmans will trample and kill fragile plants.
Feeding & supplements - Crickets should be sized smaller than the distance between frog's eyes and gut loaded with carrots, lettuce, and cherios cereal 24-48 hours before feeding frog. Best food are not dyed night crawlers available from Walmart or local bait shops. Depending on your frog size you can cut them from pointy end into mouth size pieces for babies, body length for 2 to 3 in. juvies, and full size for larger frogs. More info on supplements in here: http://www.frogforum.net/food-feeder...schedules.html.
Lija mentioned enclosure size to frog size ratio and that is important too. A too large enclosure will stress a baby Pacman. How long is your's from snout to vent? Lot's more info on Pacman care in here: Frog Forum - Pacman and Horned Frogs - Ceratophrys - Care and Breeding.