Mineral oil doesn't do anything, as the sulcata's shell is relatively impermeable. This also clogs pores, and causes a series of problems. Also, your torts will attract dirt much more quickly.
It is entirely normal for sulcatas to have a semi-soft spot at their naval until at least a year of age, sometimes longer depending on the animal's growth rate. Just make sure to supplement the tort's diet with repcal (you can find it in most petstores, and use it as directed, unless you keep your animals outdoors, in which case use it sparingly).
I tend to favor kiddy pools for indoor tortoise enclosures. They're light, spacious, and easy to clean. I generally line these with a soil mix (one part sand, one part peat moss, one part top soil). Put plenty of shelters and interesting hiding spaces in the enclosure (make sure the tortoise has something to do, other than pace the fence). Make sure the tortoises can't flip over, especially under a heat lamp. These usually need to be changed out once a week, or once a month with spot cleaning (but this is very tedious after a while, so I tend to go with once per week). Once these guys get some size on them (four to six inches), give them a space outdoors if possible. Once they reach that size, keep them in something as large as twenty by twenty, with plenty of shade and cover. Once they get larger, give 'em the better part of an acre. They will cover it, ten to twenty times daily when they're big.
T.G.
