Yes, DNA testing will work. However, uros are usually dimorphic enough to tell the male from the female, so in my opinion, it's a waste of money. Males will get hemipenal bulges, and usually exhibit femoral pores and brighter colors, so you shouldn't have too much trouble knowing.
As far as interbreeding, I'm working on breeding a male mali to a female Saharan. There aren't any pre-zygotic barriers I know of, I've seen them *ahem* get freaky, so it looks like everything fits, and such, but it's possible that they have a different number of chromosomes, or some other post-fertilization barrier. I've never seen any research on it, so I'm just going to go for it and see what happens. My male isn't fully sexually mature either (he could've fooled me, the little hornball), he's only a year still, so I probably won't have any answers for you in the next year or so.
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April
1.1 Mali Uromastyx- Embrodak, Scheherazade
2.1 Mountain Horned Dragon- Beren, Luthien and Tinuviel
3.0.5 Hermit Crabs- Violet, Polly, Jennifer, Pigwidgeon, Trogdor, Hedwig, Penelope and Sinistra
1.1 Five lined Skink- Leela and Fry
2.0 Bettas-Nuala &Lucien