My suggestion, and I think others would agree here, is that if your animal isnt eatting within, im gonna say another week, you need to get it to a reptile-savy vet, not just the closest, cheapest vet you can find.
Dont wanna spend the money? Well, if your dog or cat just stopped eatting you wouldnt try to force feed them before checking for internal problems, would you? There ya go.
And yeah, you def need to fix that cage. I feel for ya, I do. I just recently spent over $1,000 on a 125 gal. aquarium and stand only to come to the realization that it was far too small and a poor environment overall. Check out information regarding "stock troughs" , which are basically large stainless steel feeding troughs for livestock that can be built around, making a great sturdy cage thats resistant to warp..... problem is, these things are quite heavy, kind of expensive (NOTHING compared to the cost of a large aquarium) and require some level of handiwork to make them into a good cage.
Heres some basic info for you to work with:
*Basking Temps: you want ambients something like 80-90 with basking spots around 130-140 (these are Fahrenheit degrees and SURFACE temps, not air temps). If im wrong here, i have no doubt someone will correct me. Humidity should be kept at at least 50%, prolly higher (though im not 100% sure with Savs).
*Feeding: If you're going with the pet store outlook, im guessing youve been given the ol' "oh that animal only needs to eat 2-3 times a week (maybe less)" by the pet store. This is wrong. You should feed your animal daily, as much as it cares to eat. Insect matter, mice, rats, chicks/quails, as well as all manner of aquatic foods (fish, crab, shrimp, prawns, crayfish) should be offered, tho rodents should make up the basis of the diet (ive heard that weanlings are rather nutritionally deficient, so you may want to stick with feeder roaches or something as the main dietary stable til your guy is big enough to take on adult feeders).
*Substrate: Dirt, just plain ol dirt. Try to limit the amount of sticks/rocks that get into your dirt, as this can cause structural weak spots, making it not only harder for your animal to dig a sturdy burrow, but actually making it dangerous in the event of a cave in. Also, I dont think it is possible to get an impaction on dirt, or at least it is much more difficult. Try feeding your animal in a location where feeders cant get themselves mixed in with the substrate, which is usually how monitors end up ingesting said matter, causing impactions and the like.
*Lighting: Alotta people here us say "130-150 degree basking" and think, "Well golly, thats way too hot dont you think?" The long and short of it is, no, it isnt. These animals are much hardier than we are in terms of heat, and its healthier for them to have a very hot basking spot. This allows them to quickly get their temperature where they want it, instead of having to spend long periods basking (keep in mind, these are SURFACE temperatures, not AIR temperatures). UV lighting is nothing more than a waste of your money and has been regarded by people that are easily considered pro's as "unnecessary". Stick with a higher powered incandescent bulb, usually something like a 150 watt flood (i think...).
*Caging: With caging and monitors, one rule comes to mind: bigger is ALWAYS better. The bigger you can make your cage, the happier your charge will be. Im not sure with savannahs, but I know other large species (Niles and waters) have a minimal size requirement, MINIMAL size requirement, or 8' long x 4' deep x 4' wide. This is very large, but honestly, if you cant afford/dont have room for a larger cage, maybe you need to think about choosing a different kind of reptilian pet. If you are willing to give the animal what it needs, good stuff. Typically, the trough is used to hold the substrate. Wood is used to build a frame around the trough, which is then covered with FRP (fiberglass reinforced plastic, sold at home depot for $30 a 10' x 6' sheet).
Tips:
*when the time arrives, get your animal used to eatting frozen feeders- they are much cheaper when bought wholesale from places like rodentpro.com and make your life alot easier, while at the same time giving you a quick and available supply of feeders.
*patience: youve got to have patience, infinite patience, with these animals. They will work with you only on their terms, and if you try to force something on them the react the way you would expect: aggressively. Take time, dont get frustrated and be ready for problems to arise and ready to tackle them.
*honestly, if the above mentioned things seem more like work to you than anything else, you need to seriously re-evaluate something: Do you REALLY want a sav monitor? Why do you want it? Is there not another reptilian charge, possibly smaller and with fewer requirements/expenses, that would better fit your situation? You really need to understand that, with optimal care, a sav monitor can live for many years and become quite large. Feeding will become a matter of hundreds of dollars over a few months, thousands over a few years. The amount of substrate needed to fill an appropriately sized enclosure can easily weigh more than a ton. Your animal may at some point become aggressive (almost certainly will with age) and you need to be ready and prepared for a large, cold blooded predator that dosnt particularly care for you.... aside from when youre offering it food.
Basically, start working towards fixing your mistakes and seriously evaluate whether or not you realy want this animal, and if you REALLY do want it, whether or not you can REALISTICALLY care for it.