Verification against EU Law

Hello,

I am planning to apply for verification against EU law for my partner and have a few questions. I am French and have been here since September, am registered, and have a tenancy contract here in NL. I have a one-year work contract but it is a unique situation as I am being paid a large stipend by a US organisation but working with a NL-based organisation. So I don't have a "real" contract. My partner is American and will be arriving in February. Before I moved here in September, we lived together for three months but my name was not officially on the lease agreement and we did not have a joint bank account. We are unmarried.

My questions are these:

1. Does my partner need to register at the municipality before we apply for verification with the IND? How can he do so without a residence permit? Is an RNI enough?

2. If the decision process takes 6 months (until we have lived together for 6 months), can he stay in the NL while we wait for the decision? Or does he have to leave after 90 days?

3. How can I prove my income if I don't have a real employment contract (so can't fill out the employer's declaration)? If we have to show bank statements, we should show that we have enough money but for how long?

4. We will be submitting the verificaition application form (for him), the registration as EU citizen form (for me), a legalised document stating that he was never married, proof of my financial situation, and copies of our passports. Is there anything else that is really crucial at this point? We will be applying by mail unless the COVID regulations change.

Thank you so much in advance for your help!