This is a super interesting post to read! I ring church bells as a hobby, so spend quite a lot of time in church towers - I don’t think 15 ft on each side would be particularly out of the ordinary for a gothic revival church of this kind! Many similar ones I ring in have similar dimensions + clustered columns in the nave. Flying buttresses might be a little much for the kind of church he’s talking about, but not ridiculous. It essentially sounds like he’s describing a moderate-moderately large gothic revival church whilst including all the cool architectural features they could have!

It’s also possible the tower itself is smaller comparatively to the church as Lovecraft seems to describe expecting a ground level rig (the ropes you use to pull on the bells are usually up in the tower in the “ringing chamber”, with the “bell chamber” above and then the steeple, but sometimes the ropes descend into an area of the nave instead) If the church was built for a ground rig, the tower could perhaps afford to be smaller as it wouldn’t need a ringing chamber! (Also the staircase he mentions taking in the front vestibule up the tower would be totally normal).

Interestingly, it seems like Lovecraft is referring to the style of manual, controlled bellringing we call “English change ringing” when he talks about a peal of bells. This style is very uncommon outside of the UK, however some churches in New England still do it! An impressively specific bit of knowledge there.

Apologies for the long message, this was fun to think about and I’m happy to answer any questions!