Well... first consider the very worst conditions (very cold, snow, heat on). At 65 MPH you'll likely be able travel half of the rated range and have a bit of buffer battery left over.
Next, consider the likelihood of NOT being able to charge at your destination. That could be because you can't get access, because somebody borrowed the extension cord, or because you're only stopping in for an hour. If it happens you might be stuck for a bit.
If you're good with both of the above then the small battery is probably ok.
Or you could also simply accept that there are some trips that you can't make in your car - and that you might have to use your wife's car. That happens to me semi-regularly in the winter. Sometimes it's just because we need to leave right after work, and I've been driving around during the day. That leaves me with too little charge to make it to the closest supercharger unless we delay leaving for an hour.
The reality is that, with the current infrastructure, there are some logistics to owning an EV. It is getting better. But if it were me, and I were cash limited, I'd take a used 90D over a new 75D, seven out of seven days of the week. There are still logistics, but they drop rapidly with range.