So with a target date fund of 2050 through vanguard you are close to 40% international equities already as well as bonds. You didn't mention in your OP if you want to hold bonds or if you are trying to go 100% equities. If you move out of the target date fund you will be omitting your 10% holdings in fixed income.

Do you think a 80/20 split S&P/International would be better for me then the target date 2050 or 2055?

If you take this route you will be reducing your U.S holdings from 3637 stocks to 507. As your target date fund holds total market vs S&P. How would would you save expense ratio wise for this move? Again I am a passive index investor so you would have to explain to me how lowering your international allocation to 20% is better. If international performs similarly to 2017 over the next 5 years and trumps the U.S will you still hold this 20% or are you performance chasing?

Overall I see nothing wrong with your suggestion, in my opinion as long as you know what you are giving up (stock holdings and bond allocation) as well as any difference in expenses. As I mentioned above, there is no correct answer. Your choice in 15+ years could choose to be the correct one or the wrong one.