I am a tenor (singing), my singing range is Bb2 to F5. I have reached D6 in falsetto, forcing myself a lot, but my voice breaks all the time, even when I only speak. My voice is not deep at all, I'd say it's male average when I speak: C3 to G3, but when I try to change into "female mode" I definitely don't pull it off.
As a girl, I lack resonance (I sound almost falsetto) and I lack good intonation: I can clearly see I am almost monotone, using only some three different notes all the time, as opposed to any average girl, who I know she'd use 7 or more different notes while speaking. My girl range is well in between the female range (F3 to B3), but I sound ridiculous and I hate hearing my voice when I record it.
Now this is something we can work with! I too was a tenor in a past life and used a my vocal training to speed the process of accessing a female voice.
Speaking in a female voice boils down to accessing the head voice, minimizing resonance in the chest, and maximizing resonance in the sinus cavities. (Hence: chest voice / head voice). This is different from falsetto, which pinches the throat to create tone. You're just moving where the majority of your voice is resonating. Pitch is not a big deal - so long as you're around A4 speaking you should have no troubles at all sounding female.
My recommendation is to get the albums of some alto-voiced female singers (Namoli Brennett, a trans singer herself, comes to mind) - and sing along with them. Concentrate on matching their intonation and timbre more than hitting notes; the notes will be easy, but altos handle their voices a lot differently than tenors. (An alto, for example, will really lean on G3 to C4 and lay off on F4 to B5, where a tenor would do the opposite.) This relearning is _hard_ and takes months to learn, but in the long run itll land you a much more believable and full-bodied female voice, as you'll have learned the singing/speaking/resonance patterns in their whole instead of simply following a quick-and-dirty guide. Since you've got singing experience it may be the best way to go as well - I know it's how I found my voice.
The intonation will come with time and talking with other girls - it just sort of falls into place. Flipping your unconscious voice into the head register will be the hardest part, but I assure you that if you get this down you'll have a passable female voice.