Depends how you define "waste of time". Given how much upset the visible rust has caused the OP, it might be worth doing something about it, if only from an aesthetic POV, especially if one might want to sell.
The adv ice has been consistent - the "upset" is not a big issue. Cleaning the rust off and painting is straightforward and effective.
Air is very compressible a small pocket of air will push some sealant up the threads but that is all.
I think your missing the point, the op requires confidence, not a slap of paint to cover up, nobody can say the true condition internally, and all advice saying 'it'll be OK " isn't going to give him that confidence.
I am not missing the point. Confidence can come from asking the question as the OP has done and listening to the answers. Not one answer has indicated there is likely to be a problem. There is no suggestion that the keel has been damaged in any way or moved - so how can there be anything wrong with the studs? The tops which have been in water have some rust but still look the same size as original. No water can get past the nut sealed to hull. There are a number of examples on this thread of people who have removed nuts and studs in similar circumstances to find they are like new. Videos and photos as illustrations. Painting the tops after cleaning is an appropriate measure to prevent them rusting and looking unsightly in the future.
It's his life and possible his family and/or friends, plus any emergency rescue people that my be put at risk, I agree he sould satisfy his concerns and be confident.
I think I qualify for that - I flew Sleazyjet the other day, and I only had to use my parachute once...I'm sure you all are very capable of smiling if the captain of your next flight said there are some rusty old bolts, but i was assured by YBW that all is ok
