Develop your m1 range up to about c#5. This may take a few years to really get access to these top notes, and even then they may not be reliable. Jon had a fantastic voice at that time, one that is very hard to emulate. I think, at that time Jon was very comfortable singing from g4 to
B4, as he hits these notes in almost every song on these days, so pay attention to that part of your range. Try to sing with some "twang". Do this by placing the sound in your nose, then manipulating it into a sound that is more pleasant and less shrill. Lastly, try to develop Jon's signature rasp across all your range. Here are some resources I recommend for learning how to get control over the sound of your voice.
1.this YouTube Chanel (https://m.youtube.com/playlist?list=...q62c27q3RLOwGI) is filled with quick tips and practical explanations that really work, and helped me gain control over my sound. Also, it is thee most evidence based, least BS singing channel on youtube.
2. A book called Complete Vocal Technique (CVT). This is extremely useful and comprehensive, and helps give you access to all parts of your voice.