Pins 2 and 4 are exactly the same. Except any heat dissipated from the device will be conducted out on pin 4 (the tab). So you want a lot of top copper around pint 4. Maybe that is your ref box?
Your capacitor location is likely fine, however I would move the input to ground 90° and put it right at the pins 1 & 3, Then I would move the other to the right of the regulator.
Why would I do this you might ask. Good question. For high frequency reduction you want the leads as short as possible. The longer the traces to the capacitor the more the capacitor effect is at high frequencies. The digital lines of the Arduino generate high frequencies..
But as I said you are likely OK but not optimum. And with the 1117 pin 1 crossing between 2 and 4 you are limited on how large you can make the topside copper which limits how much power you can dissipate in the device.
John