For the OP per diem is for meals and incidental expenses such as tipping baggage handlers. So I can see why they are saying taxi or uber tips go there. The 75% seems to be std. now for first and last day of travel. The other option which is PITA is to submit actual expenses. Given everything I would list Friday as my last day of travel because you are traveling on Friday.

FWIW I just got back from a government trip where I got stuck with part of the bill because my hotel was outside of rates. I was visiting two different sites so I combined them to save time and money. One site was okay with the extra hotel expense because the flight and car were half the cost, the other did not care about the that saving so stuck me with hotel overage.