I put it in Brewfather, it gives a pre boil volume of 7.73L.
I don't sparge and it gives total starting volume of just under 9L. Try entering your recipe.with sparge option - still think your pan will be too small though.
I‘ve had success doing similar BIAB in the past but it’s very tight, Just top up as mentioned.
I’d be more inclined to do partial mash or extract in that size pot though. The other option is to mash in a bucket/FV and then pour the wort into the pot/kettle to boil. Note you can top up with wort this way as the level in the pot drops.
Finished the brew a few hours ago, I did the dunk sparge suggested by @Agentgonzo, worked great. Wouldn't sweat using a 7l pan again. Plenty of room for a vigorous boil also, but a bigger pan may be on the cards if I do these smaller brews more often. I noticed the process start to finish is much faster and clean up much easier than the 25-40L batches I'm already used to.
I have also started doing small batches occasionally (full BIAB), got a 14L stock pot for around £20, boil volume around 9L so plenty of room and no spillages. I agree with you it's faster, clearly with smaller volume, find it more relaxed than 5 gallons.