The $100,000 limit applies to each person, even if you filed jointly.
See Joint Returns in the Instructions for Form 3520: If you and your spouse are filing a joint income tax return for tax year 2021, and you are both transferors, grantors, or beneficiaries of the same foreign trust, then you may file a joint Form 3520. See also a previous relevant discussion here.
And, on Form 3520, you'll note that there's a checkbox on line1i, If you are filing with your spouse a current-year joint income tax return and a joint Form 3520, check this box.
The instructions for Line 54 in the Instructions for Form 3520 speak to the aggregation of gifts:
To calculate the threshold amount ($100,000), you must aggregate gifts from different foreign nonresident aliens and foreign estates if you know (or have reason to know) that those persons are related to each other or one is acting as a nominee or intermediary for the other. For example, if you receive a gift of $75,000 from nonresident alien individual A and a gift of $40,000 from nonresident alien individual B, and you know that A and B are related, you must answer “Yes” and complete columns (a) through (c) for each gift.
As far as your last question, there's no indication of what the IRS would assume.
