they said it was built but sat in Fremont, so I’d expect it to not be on any ships currently sailing
based on past history the stuff they told you is very improbable. Tesla don't let (or more likely can't afford!) cars sit around at the end of a quarter. After the last boat sales, in time to sell the cars in the EU by end of quarter, they stop sending any more over and start shipping from factory to Canada and USA. Before Christmas they put a tent up on the dock in Holland and delivered to customers straight from there! (Cars are charged on the dockside, after arrival from USA, so all they get going via the service centre is a wash ... the windows were still wet on mine when i picked it up, it had been on a transporter 30 minutes before ...)
Plenty of previous of Tesla folk making stuff up. Its a pity, and would be much better if they said "I don't know" or "I will find out", so I'm afraid your car could be anywhere ... the fact that you have got a hidden-VIN is normally a very good sign of it being imminent.
If car arrives, and you don't have wallcharger, then if you can only charge off 13 AMP plug you will get about 9 MPH, so that may be enough to tide you over (if you can use public chargers / Supercharger ... or @ work?? for any longer trips).
A Better Route Planner useful for trying out your common longer distance routes. Set up the make / model, and then choose starting battery %age and e.g. Temperature / Wind to simulate Winter / worst case, and see where it suggests you could "refuel" and how long it would take.
I don't remember what the requirements are for "proof of ownership" for the OLEV grant, or you could consider a non-OLEV wall charger. The OLEV process itself seems to add-on some cost, so sometimes non-OLEV can work out not a lot more (particularly if long / difficult wiring involved), and may have other benefits, but maybe you could be getting on with that soonish? Is your main fuse big enough, or might that need upgrading? Stuff like that can introduce delay too ...