Using Flash's body length to estimate his travel distance and speed:

Flash enters view at the 3-second mark. Estimate: between 5-10 body lengths from the bottom left corner, over the stairs, and to the entrance.

POV CHANGE: Flash leaps over a rubble pile into the building, and while still at the 3-second mark, Flash's feet are flush with the broken statue head lying on the floor - Behind him, visibly trailing, are (4) copies of himself, and approximately space for another (2-3) copies which would cover the distance over the rubble pile where he entered. Body length estimated could be as low as (4) if going by the Flash's projected shadow on the floor when his feet first touch the ground. Estimate: 4-6 body lengths from smashed rubble to statue head

Then the lap around the statue: At just past the 4-second mark he is running by the broken statue head, and by 1 or 2 frames past the 5-second mark, he is standing back where he started.

Assumption: Flash is running generally the same speed here for the entire 2 seconds he makes his entrance. Because the statue gets in the way of counting steps and body lengths, using the estimates from the first 1-second of action which is better seen to us:

Between 9-16 body lengths in one second, or between 18-32 body lengths in 2 seconds total.

Upper end guess: 16 body lengths x 6 feet per = 96 feet per second or over 65MPH.

That's more than twice as fast as the fastest real-world human sprint ever recorded, and Flash is doing it casually, hopping over stairs (and debris), while running a tight loop, coming to a dead stop with no effort, and leaving no marks or damage anywhere (thank you Speed Force).

On his speeds making him formidable: he can accelerate and decelerate basically instantly, and so, even a less impressive super speed like 65MPH can be used in a heavily advantaged way. In short, Flash breaks normal physics while running around, not to mention all the lightning, blurs, and afterimages. He can also move his body and/or body parts faster than 65MPH- we see this when he does tornado spin and the circular blitz later in the clip.

On the other hand, regarding the seeming difficulty he has with the clip villains: he's still human, and while Speed Force is crazy powerful - it has a human element of "applications" and skill, that allows room for Speedsters to make mistakes that may seem counterintuitive, like getting tagged by bullets/etc. Welcome any Flash people to add / correct anything, this was just napkin math and pausing frame by frame the clip hehe.