Good tamp pressure will only come with practice. There are tampers out there that are calibrated to the desired pressure and will click or do something to help you know when you reach the desired weight that can definately help you with your consistency.

Realistically the exact pressure doesn't matter too much. You kind of hit diminishing returns at around 30 pounds. It's a good weight because it allows you to tamp pretty hard to lean into it and more weight isnt going to change much because the grounds are well packed and will already spring back slightly on their own.

Consistency is king though. If you can do the same thing every time you tamp than that is one less variable you need to think about. The grinder is 90% of getting good extraction. Your tamp is the same as yesterdays then that means the grounds have changed. Maybe the coffee has dried out a little bit more so you want to try to get a better extraction of the oils. A finer grind gives more surface area and will bring out more flavour. A finer grind in the same basket may mean you need to change how much coffee your grinding. If you have a grinder that doses by times than a finer grind will put out less coffee. Not only because it's smaller and will look like less but it takes longer to grind finer so you have to account for that.

$20 from amazon will give you a 0.1gm scale which will remove the second major variable and will really help you take your coffee up that notch. Hario sell their poreover coffee scales for about $60 but for less than a quarter of the price they also sell a pair of smaller unbranded scales that are much more accurate at higher weights( high enough to hold a glass and a handle full of coffee, I think they're 0.1g acurate to 1500gm. They're fantastic and it's hard pressed to find a cafe around her that doesnt have a couple of pairs. Those a timer and consistent tamp really make espresso so much easier