Most of these studies show that the effects of HRT on the older population are not well documented, due to few people available for evaluation. There just are not that many of us.
Having said that, there are many of us here on Susan's Place who started transition after the age of 50. For my self, I started at age 64. I am now age 69. From my personal experience, the effects of hormone therapy are the same for me as for many much younger people. The important thing is to not have any cardiovascular disease in progress, monitor liver and kidney function and let your doctor adjust the dose based on blood levels.
Many doctors prefer trans dermal, injectable, or sublingual bio identical Estradiol. Adding Progesterone does have some advantages, but many doctors still consider this as optional. Using a Testosterone blocker has advantages, but is not necessary after genital surgery or with prolonged Estradiol therapy, as shown by blood levels.
When you will no longer be able to go to the beach topless is really variable. Some of us respond rather quickly and others just barely respond to Estradiol when it comes to breast growth. Transition can be very embarrassing when you begin to show, but are not ready to fully accept the new gender expression. For myself, I wore a swim shirt to keep covered up as much as possible.
Some of us are lucky enough to have an accepting spouse and others do not. My marriage did not survive my transition, but we had problems for other reasons as well. Many women just do not want to be married to another woman, ether cis or trans. Other women have so much unconditional love, that the external appearance is not a major concern and there are many variations in between.
If your wife is expressing reluctant support, then there seems to be issues which need to be discussed between you and your wife. I recommend a professional counselor before proceeding with transition.