Google Workspace sender stuck at SCL=5 to all Microsoft-hosted recipients

Sending email from a new domain via Google Workspace. All mail to Microsoft-hosted recipients (both Outlook.com consumer accounts and Microsoft 365 Exchange Online tenants) is being routed to junk. Authentication passes perfectly on every message. This appears to be a domain reputation cold-start issue and I am looking for guidance on how to resolve it without waiting 2-4 weeks. Affected recipients are all Microsoft-hosted recipients tested (Outlook.com consumer + Microsoft 365 Exchange Online tenants). Please help me!!!

Confirmed via X-MS-Exchange-Organization-SCL: 5 and delivery header dest:J;OFR:SpamFilterAuthJ;RF:JunkEmail on all test emails including ones with normal subject lines and body text. Content makes zero difference to the score.

What has already been done:

• SPF hardened from ~all to -all
• DMARC upgraded from p=none to p=quarantine
• IP confirmed not listed on Microsoft's delist portal (sender.office.com)
• Domain confirmed not listed on Spamhaus DBL or SURBL
• Domain registered with Google Postmaster Tools
• JMRP enrollment attempted — not available to Google Workspace senders as SNDS requires IP ownership
• Outlook.com Postmaster support request submitted