@womenprofession Check out this article. It's the best I've ever found on the subject: How Much Water Should You Drink? Here's What the Science Says. (precisionnutrition.com)
The hydration chart near the bottom is really helpful...
@mbai22 How did you fix your issues with your left shoulder? That's a problem I'm currently dealing with.
It sounds like you're doing great. Especially for your age, you're probably easily in the top 0.1% of strength for a 78 year old.