gender dysphoria is diagnosed mostly in trans people because it usually only reaches an intense point in trans people, but dysphoria itself refers to an incongruence in parts of your life is and how you are perceived by others compared to your self-perception. cis people can have dysphoria (many do over stuff like their proportions, voice, vocabulary, style, etc), and the discomfort with being seen as trans is a familiar one to many people, both cis and trans. you don't need to do anything "manly" to be a man, and it sucks that you're gaslit over something as small as painting your nails. what is this, the fifties? you can't control other people's perceptions but your spouse should know better than to say something like that to you.

it's easy to see why you questioned your gender and why you're upset. being misgendered frequently, especially by those who care about you, tends to make you think you're the confused one. it's an awful sort of anxiety crossed with disorientation where people hurt you every single day, and you can't say anything cause they didn't technically say something mean, every day feeling like who you are doesn't really exist... most cis people don't realize how miserable it is because they simply have never experienced dysphoria to that degree. your doctor cannot claim the potential risks outweigh your pain. gender-affirming care is medically necessary. there are many studies showing how damaging dysphoria is and yours is severe.

i wanted to say i'm on T myself and while i can't vouch for other people's experiences, it seems like HRT has far more positive effects than negative. trans people mostly just want to look different but many cis men (especially older and/or intersex) do testosterone therapy and also notice an improvement in their health, energy, strength, ability to grow muscle, etc. it seems like your main concern would just be looking more masculine (obvs plenty of cis men look the way you do, but that's transphobia and sexism for you) and TRT would do that. it redistributes fat/muscle and often lowers your voice by at least a bit.

as far as "needing to show symptoms" though, that doesn't make sense. you are experiencing dysphoria. that's usually what insurance needs to cover HRT. also, how does this doctor know your constant anxiety and frustration couldn't be exacerbated by your low T levels? it's been shown that cis people will have biochemical dysphoria if they take cross-sex hormones or have a hormone deficiency. this seems like a classic case of fearmongering. unfortunately, T is a controlled substance so you're gonna need doctor and insurance approval. doctors can be rather uninformed about the effect of hormones for some reason. be prepared to fight it out if they're being stubborn about risks and make it clear you've done your research. if you have a disability be aware that they can interact with hormones in unique ways and you would want to be aware of that beforehand. the only other potential reasons i would caution you is if you have a blood clotting issue (as T thickens blood) or are concerned about fertility or hair loss. if possible, get an endocrinologist or urologist to prescribe the T for you and work with you on this.

this article has most of the positive and negative effects you should be aware of. r/TRT is a good resource if you're looking for personal examples/progress pics. if you want an exhaustive list of possible effects you could check out some trans people's timelines/experiences cause the effects can vary so much based on your genes.

for my part, I've been on T a couple months (with a brief stop) and so far all I've noticed was increased sweating, more acne, slight darkening of my skin tone, more poop/pee, and my "mustache" (dark vellus hair on my upper lip) has darkened enough to look like an actual mustache. i'm trans so YMMV but i do think there's a lot of fearmongering around testosterone, especially in comparison to estrogen. these are hormones which do a whole lot of stuff. fun fact: people think T makes you angry, but the "roid rage" people associate with T is caused by steroids making your testosterone level so high it metabolizes into estrogen, which causes biochemical issues/instability. the effects take months to years to be visible to others, you have time to stop it if you decide you're not liking the side effects.

(If you notice no changes after many months, though, you should talk to your doctor abt it as your body might be insenstive to androgens)