You should definitely stop using something as harsh as DMSO on your genitals bro. Most of the T products I've seen that are made for testicle application are usually lipid based. A gel could also probably work.
But I wouldn't use anything stronger than propylene glycol and glycerin down there. Maybe a touch of everclear if you need to increase the solubility of the solution. DMSO practically gives you a low-grade chemical burn everytime you use it. Don't want that going on your balls or penis.
Also, I don't mean to prolong the conversation in the wrong forum section, but I feel you should probably be aware of this. DHT to to "grow things" down there should be expected to help minimally at best. It's like asking why taking growth hormone won't make you taller. Well, a lot of this has to do with your DHT levels when you were in puberty, not so much post-puberty.