Confused about preboil gravity

Hi folks. Did my second AG yesterday and had an issue I don't understand. I mashed in with 15 qts. and after an hour these runnings had a gravity of 1067. I am shooting for 1049 so I just figured after sparging it would be right (correct assumption?). However, after sparging 5 gallons I was reading 1014. At first I assumed I was misreading somehow given the drastic drop, but I measured a couple of times and kept getting 1014. Even accounting for temperature adjustments this was a drastic drop.

I think I did a couple of things wrong, first I think I didn't let the sparge water sit long enough (I was batch sparging by the way). Second I should have stirred the sweet wort after sparging before taking a reading. Also, 5 gallons seemed like a lot to sparge with to me but I was following BeerSmith. Lastly I think I just f'd up somehow with my readings. I bought a refractomoter later that afternoon I was so frustrated. I'm not sure how much sweet wort I had after both runnings but it had to be around six gallons

I boiled for two hours to try and correct the low gravity. I ended up with about 3.5 gallons of wort, although I was happy that the OG was 1054 since I was shooting for 1057.

Thoughts?

Batch sparging, you don't need to wait after you put in the sparge water. Just stir it up really well and then vorlauf.

I think your issue must have been not stirring well before taking your reading.

Your OG at the end of the brew day seems pretty much in line.

this is normal,the first runnings will be crammed with sugars and have a high sg and towards the end of the sparge you'll have most of the sugars out thus the low sg.
to get a true reading you have to mix all this up as the the high sg wort is denser and hangs out on the bottom of the kettle with the lower sg stuff floating on top, the convection in the kettle mixes it all during the boil hence the reading you were anticipating post boil