My husband had several part time jobs in 2020 (married filing jointly). Do I need to include all w-2's when filing taxes, or just those over a certain amount?

You have to report ALL your income, no matter how small.  Even $1 of bank interest you don't get a 1099 for.  So yes you need to enter all the W2s.  The IRS gets copies of them and will be expecting to see them on your return.

... and there is a lot of information on the W-2s that TT uses to inform other situations, like in what state the income was earned and several different codes in Blocks 12 and 14.  It is a good idea to enter every bit of information from every block of every W-2.