mevatel issur lechatchila- I believe the shach allows lach belach.
fatty and lean meat- Not sure where, but a long shach, taz, nekudos hakesef, taz mahadura tinyana on it.
Gelatin-
Reb chaim Ozer was one of the mattirim, along with Rav Yechezkel Abramsky. Feel free to read thru is and summarize the key points for us baalei battim, especially if he clarifies if dry bones or even wet marrow-filled bones, length of time for processing, and any indications if pig skin would be different or if he would agree to the yabia omer.
Sam2, this is literally what they call toeh bedvar mishnah. BTW ohr veharoteiv is one of my favorite perek names in shas- “skin and sauce”. Still not sure what the hava amina was- if everyone eats it as a snack, it’s clearly not achshevei. Leather boots are only eaten in cases of seige, but people WANT to eat pork rinds- it’s a booming business. clearly food.
And even in a brisker lu yitzur world that the pig skin itself was muttar (which it’s NOT, the cracklins are fried in lard.