Is there a reason you can't take oral estrogen?
Regarding the Idea that less estrogen is needed when you get older, a) there is no evidence to support this, it is an opinion that is widely expressed and has even made its way into clinical guidelines, however there have been zero clinical studies investigating this, and b) you are 50 not 85, so in menopause terms you are a spring chicken.
As well as your quality of life, those bones have to carry you around for hopefully another few decades, so do factor in longer term benefits as well.
You are in a very fortunate position not to need a progestogen.
In your position I would definitely consider oral unless there is a medical reason why not.
I am on oral estrogen in the combined pill Zoely, and I will be continuing on oral hormone therapy when I no longer need menstrual suppression.