So with all of my fields combined, I believe I will go over the 300 fields unless I create custom modules to lessen them. I am planning on creating a phone module and an address module. I understand the lookup feature, but how can I do this in batch? To click lookup record for every single lead is quite tedious, especially for thousands of leads/contacts. If there's a better way, please let me know!

Also, is there a way to show the contents of the custom module in the lead module without having to click a link? I'm concerned that there will be a lot of going back and forth if you have to click a link, leave the lead record page, then go back to it. 

Thank you for your help!