Hi
The 3hr A time and 2 hr nap on that looks great! Looking at your day, I think the 15min car nap meant she wasn't tired enough to nap at 2, but then got OT with a long afternoon. I'd try for 3hrs A time before both naps again (hopefully she'll manage to stay awake for it!) and see how she does.
And yes, EBT is fine & often necessary in the 3-2.
You might find that in the early stages of going to 2 naps she can actually do more daysleep and still do a good night...I'd be tempted to try up to 2hrs for both naps at first (with her awake by 4pm) especially with her being only just 5mo so doing this transition a little early, and see how the night goes.