If the recommended software is not working great (it hasn't for me as well), scrapebox is reliable.
You just need a couple millions of tumblr blogs scraped. Try and scrape old tumblrs. If you use google to scrape make the time setting to be at least 1 year old. You can play with the time interval.

It's just a game number. After that is time to put in place a good workflow to check 404's, metrics and actual availability.
With the new MOZ update, now I can get easily PA+50 and sometimes up to PA80.