Startup terminating me. No strike price set yet. Am I screwed or "future proof" on my equity?

​I need a reality check on my stock options. I’m being terminated from an early-stage startup on December 15th. I have a 0.5% equity grant in my offer letter, and based on my time worked, I have vested 0.33%. ​Here is the specific situation that has me confused: ​1. No Formal Grant or Plan Documents My offer letter states the grant is "Subject to Board Approval", but I never received a formal Stock Option Agreement or a copy of the Equity Incentive Plan. The offer letter itself is the only document I have regarding equity.
​2. No Strike Price Exists The company has only raised money via SAFEs. They have not done a priced equity round or a 409A valuation. Because of this, there is no Strike Price (Exercise Price) established for my options. ​3. The "Silence" in the Contract My offer letter does not mention a "90-day post-termination exercise window" or any deadline for when I must exercise my options after leaving. It is completely silent on expiration terms. ​My Theory (Am I wrong?): Since there is no strike price, I physically cannot exercise my options right now even if I wanted to (I can't write a check for an unknown amount). Because the offer letter doesn't list an expiration date, I’m assuming I can just wait indefinitely until a strike price is set in the future to exercise. Essentially, I feel like I'm "future proof." ​My Fear: Is this a trap? If I leave on Dec 15th without a specific agreement, does standard startup law (or the unseen "Company Plan") default to a 90-day window? If so, does that mean my options will expire worthless in March because I still won't be able to buy them? ​The Question: Does the silence in my offer letter actually protect me, or do I need to force them to sign a "tolling agreement" or extension before I leave to ensure my equity doesn't vanish? ​Thanks for the help.