Good to hear you're interested in sulcatas. I think you'll find they're a very satisfying and very surprising pet. Even when I was twelve and got my first sulcata, I had no idea how big the guy would get. Sure, I had read about a two hundred pound tank, but my sole instinct was as to how "cool" it would be. Now, it certainly is cool, but it is also a lot of work.
As to your first question regarding humidity, sulcatas don't need much of it. The means by which they provide humidity is by hiding. Sulcatas must be able to create their own humid micro climate, and they achieve this in a close fitting shelter. These tortoises also burrow to achieve this micro climate, and burrowing within a shelter is not at all uncommon. Despite their lack of humidity requirement, I've generally found sulcatas to do rather well in humid environments, so long as there is plenty of warmth to match. If your local climate is too cool (regularly below seventy degrees F), I would recommend indoor enclosures, or simply that you consider another species of tortoise. Keep in mind that sulcatas get very large, and indoor enclosures are a messy option. I've personally never attempted creating an extensive indoor environment, but the luxury of South Texas weather permits me such privelege. Your climate conditions will determine how you should proceed.
Always buy an older tortoise, the older, the better, generally speaking. So long as the animal is beyond the four inch range, they are usually bullet proof. Hatchlings these days are not to be trusted in my opinion. Two summers ago, I purchased ten hatchlings, and none of them survived the summer, all of them becoming listless, inactive, and despite over five hundred dollars in vet costs, I lost all of them. Considering that these animals in the wild have a ninety eight percent mortality rate, it is best to see which ones start growing and thriving.
As for diet, natural graze is best. During the summers, I only feed large quantities of lettuce, zuchini, kale, collard greens, and other assorted greens every two days (avoid spinach, rhubarb, corn, alfalfa, and most fruits, as these contain too much sugar, protein, or mineral binding compounds). If your local market sells dandelion greens and/or spineless prickly pear cactus pads, tortoises also eat these. I've noticed that the younger animals tend not to favor the cactus, but my older boys take it with relish. During the winter time, supplement and feed with less frequency. Determine this by the animal's weight (you want to minimize weight loss; weight gain is not typical during winter months, as the shortened day length tends to produce greater inactivity). It is entirely possible, and highly advisable, to grow plants for your tortoises. I have several mulberry and hibiscus bushes in my backyard (tortoises love the leaves and fruits of these). I spread dandelion seed everywhere, along with buffalo grass, winter grass, and rye grass seed. I also have several althea plants, which produce prodigious amounts of flowers during the summer months that all tortoise species seem to love (I've kept russians, redfoots, yellowfoots, hingebacks, greeks, marginateds, and sulcatas, and all of them love the flower of this plant).
Calcium supplementation depends upon local soil conditions as well as the frequency of access to sunlight. My tortoises spend most of their time outdoors, so I generally supplement their diets with Herptivite and Repcal every other feeding (i.e. once per week). However, if your animal is indoors and fed a larger proportion of kitchen greens, supplement at least twice per week. As I said, soil conditions determine the amount of calcium supplementation required. South Texas soil is riddled with limestone. Ergo, all of the grasses and plants in the enclosure are full of calcium.
I tend to stay away from processed foods with sulcatas. They are too expensive, especially compared to greens. Also, they are too high in protein. In addition to this, sulcatas tend to develop addictive type dietary habits, refusing all greens in favor of commercial diets, fruits, or whatever high nutrition food offered. Perhaps as a treat, they can be useful, but even as such, I don't see this going over too well. You want to make your sulcatas work for their food. Keep in mind that in the Sahel regions where these tortoises come from, there are not fruit trees or caring humans with monkey buscuits in their overcoats. Their home is a region in which survival is a daily struggle, and where thorny bushes, dry grasses, and succulent plants form the bulk of their diet. If you want to toss them a treat, grind up some squash. When they get big enough, smash your jackolantern in your back yard (removing accumulated wax, ofcourse) and watch them go at it.
I generally don't use uvb bulbs, though I do utilize them during the winter months with my younger tortoises. I use long reptisun tubes in conjunction with infrared lamps purchased at home depot. I change out the tubes every fall. I have no experience with compact, combined heat/light sources. Keep in mind, however, that there is no substitute for natural sunlight. Every animal I have seen raised under the sun looks infinitely better, stronger, and livlier than any beast kept in an indoor enclosure. If this is impossible, perhaps you should consider another species, such as a russian tortoise. However, if you have the acreage and the sun on your side, sulcatas could be right for you.
