There are many, many people who get radiation in the 70’s. I would not fear this for you, as @raebaby and others have said, some into their 80’s.
You may or may not be recommended for endocrine therapy. This depends on your specific biopsy results, every person is different and every persons choices have to be a cost vs benefit decision for their own life. I would beg you not to make decisions on someone else’s experience. Not every breast cancer patient needs or benefits from hormone therapy, and not everyone who takes it has side effects.
Stage 0, definitely means you have more leeway in choices than a more advanced cancer. Did they find this on mammogram? How are you feeling about it?