You haven’t indicated what that amount of work really is. Most of us aren’t data miners so 70,000, 700, 7,000.000.000 are not that different. He offers $30, what is YOUR price? What % of your price does $30 represent?
If it were me, anything less than 50% of my $$ value is a hard eff off - unless they are adding genuine value in another way - and be sure they will as a buyer offering a date with Kylie if I do $500 work for $5 is not at all likely to eventuate.
Anything between 50-99% of my $$ value is still dubious as to make an offer on Fiverr one commonly has already probably halved the real value of that job.
So my advice based on what you have already said, kick him to the curb hard as he is not a customer, merely a sneaky thief. Once a sneaky thief, always a sneaky thief. Find a real customer who will value what you do for them.
Easier said than done I know well. But as long as you don’t value yourself properly snakes like this will hover around you, taking advantage, yet returning nothing.