Yes, first thing is work on form so make sure when you are in the hang position that your scapulas are set and flexed, your grip should be high up on the bar so you are not just using your fingers. First work on your volume, then refine your form. If you can’t do more than 5 pull-ups then I would also recommend using a resistance band by wrapping it around the bar and placing your foot in the band

There is not a specific requirement, some people start not being able to do any and use a resistance band in order to attain the numbers they need. Most will repeat the program as they progress and are able to do substantially more pull ups the second go around. Just realize there will be some extra work you need to do in order to

The biggest thing that helped me doing pull-ups and getting my numbers up was to build up my grip strength by hanging on the bar longer than just for my pull-ups. For example, just hang on there for an extra 30 sec and do reverse shrugs where you flex your back to make your scapula retract if that makes sense. Additionally, I am not sure exactly how strict you are being with your protein intake but that is also a big factor that people end up neglecting.