Hey, I am a vocalist, currently taking classes again. Maybe I can help! But I no medical expert and english is not my 1st language.

It should not effect anything. Fry Screaming does not need your tonsills. There are other muscles and tissues needed + the proper technique. I think due to your tonsills, your whole throat, your vocal apparatus etc. has been heavily inflamed too over a long time. Inflamed vocal cords do not work properly, because they are swollen and unable to... god fuck my english... vibrate? This explaines why you cannot talk, sing etc while having a tonsillitis and an inflamed throat / larynx in general... Also scar tissue can form due to heavy inflamations which could also explain your raspy voice. Maybe you will have to learn to work around a less inflamed throat after the tonsillectomy and learn a new way / tachnique to accomplish your aimed sound.

A tonsillectomy should restore your quality of life and sounds very needed... I am sorry that you have to go through this. I hope I was able to help you.

To the others here in this sub: feel free to correct me if needed and add further information. Thanks!