Its stil a bit early, but it is looking female-ish to me.
You've got some major problems there. Most of the advice given in pet shops and online is all wrong. You've tried very hard to give your tortoise an excellent environment, but you found all the usual typical wrong care advice. I hope we can help before it is too late.
The indoor substrate is terrible. Whoever thought is was a good idea to encourage a tortoise to eat sandy substrate by putting little bits of calcium in it should have their head examined. That is lunacy. Also, the tortoise should never be on a sand substrate. Sand is a serious impaction risk and also a skin and eye irritant. Finally, you are using the wrong type of bulb indoors. The MVBs are not reliable as far as UV output, and they cause pyramiding, which you have a little bit of.
Start here and look for the care sheet and the heating/lighting breakdown at the bottom:
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Don't get hurt inside over stuff you didn't know....the folks here are only trying to make life better for your guy. He looks great, where did you get him and did you get him as a baby?