Transitioning will take time, I don't really know how long people take before they say "I'm done!" For myself, I believe it'll take me three years before I take the final step. But, even after SRS or Orchiectomy, if you plan to go those routes, you're still going to have to take hormones after. Body hair and beard removal takes a long time, over a year usually, it's expensive and can be very painful depending on the sensitivity of the area. You're going to have to decide if you want to commit to the process because it doesn't just involve the HRT pills. I'd say you never know how you'll react until you try, but that's terrible advice and you should make sure you are serious because there are permanent changes.
HRT isn't really a panacea for psychological distress, estrogen can cause you to fangirl at one moment and devolve into a hot mess in the next until you become more accustomed to the change in hormones. Yet, simply starting my HRT was such a huge relief, I've been able to hold onto that knowing I'm slowly coming into myself. The caveat: I had no intention of turning back to where I was before, it was not a good place. Essentially I guess I'm saying I don't get what a "partial transition" is. You could take anti-androgens only, some people have said it has a predominately mood balancing effect by blocking your testosterone production. However they have little physical effect on their own to my knowledge, which wouldn't necessarily help with your body image over time, and I'm pretty sure you will still become sterile over time.
While I don't know your significant other, there are probably a myriad of reasons she hasn't discussed with you. She could be unaware of them or at least the underlying roots of why she is reacting in this way, she could be sparing your feelings, and/or ashamed of how she feels. Regardless, your relationship will evolve through your transition for better or worse, but I'd highly recommend you seek counseling that can include her, as well as spend time educating her about transgender issues and gender dysphoria. The better she understands where you are coming from, the less likely she will take it personally as a slight or a manifestation of her undesirability.
It also seems like she may be worried about the attention you might attract if you start presenting fully immediately, especially since you stated you do not pass. Unfortunately for us, not blending in is a serious problem that can become dangerous. It might be hard for her to associate with you in a social setting until she grows more accustomed to your being transgendered. I guess it really depends on whether you focus on your relationship or your transition. Even better would be if you could find ways to include your significant other; to make her feel less like you are abandoning her to pursue your own path, and more like you want to take each step lockstep, her beside you.