I'm sorry about your uncle.
A few of the things you list could be due to the hormone therapy - acne (but usually only when starting the treatment), dry skin (may need a moisturiser), muscle weakness (but seems a bit soon for that to be noticeable).
Ulcers/swelling in lower legs could be a side effect of the cancer due either to blocking lymph nodes or impacting kidneys. However, I wouldn't expect that to start up or get worse when recently started on hormone therapy (if anything, the opposite), so may be completely unrelated to cancer or treatments. Could well be due to heart problems caused by COPD. If he spends much of the day seated, he should have his feet raised when seated. Ideally, he should be doing some seated exercises, particularly of his legs. Might be worth seeing if you can get a few visits from a home physio if you think he would take any notice.
This doesn't explain all the symptoms you describe, and in any case, they should be investigated, probably by GP initially, although you should mention it to oncologist too. There might be a single common cause.