From my experience latex will seal the ends, but not using spray paint. I suppose it would if I had put more than 2-3 coats on it, but I figured like you that would be plenty. Anytime I use latex I get a roller and roll on 2-3 heavy coats. I am usually using whatever paint is old and I want to get rid of. I am also doing it while it is still in log form so I am able to make a mess and not have to worry about it.
Sounds like it should be fine to me. Whenever I"m curious about support on something I'm building, I use the Sagulator to assist me in my decisions. It's primarily for shelves but, I find it helpful for tables as well.
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