hi,
thanks for all the responses,
i didn't post this before,
i did search for posts like this before posting, and didn't see any direct answers from people who have tried it.

the car did start fine on that trip with about B50 biodiesel,
but now it has B99 in the tank, and at 47F it's not starting, it's just a slight surprise, it was starting great otherwise, i'll probably go back to petro diesel til winter's over, or do more trial and error with varying blends of biodiesel.

i did try the 2-3x repeat on glow plug.

so as far as street parking in a city, without a driveway, away from outlets, it does seem like a generator would be the most direct solution, either that $120 700 watt one, or a honda 1000 or 2000 watt, a 2000 can be rented for $50/day.

jumper cables from a 2nd car plugged into a modified sine wave inverter and plugging the block heater into that could be a much more compact option, but it would require a 2nd car hanging around for an hour...

oh, someone on another forum suggested using a flameless tent heater, running off a propane tank, they're supposedly safe enough to use in a tent... which would be handy on a camp trip too...

there are diff styles but one looks like this, attached.

it's much smaller than a generator, but i wonder if it would work... nobody had posted that they actually tried it...

Attached Thumbnails

 

it turned out to be the battery,
which makes me wonder, i saw on another post someone modified their car to not draw power for glow plugs when just playing the radio, to conserve battery,
it wouldn't be drawing that power after shutting the engine off and keeping the radio on, would it?

Did the battery fail ( like a gas tank with a hole in it ) or was it discharged ( gas tank that is empty but otherwise good. ) ?

when the car wasn't starting I thought it was the cold that day, and the headlights and radio seemed to be working. the next day it was slightly warmer, but it still wouldn't start, then I noticed the radio and headlights wouldn't stay on at the same time…
i tried jumpstarting it, which didn't really work at first, but after a few times and letting the glow plug stay on for a full minute while plugged into the over car, it started up.

the shop in my neighborhood as well as the autozone tested the battery and said it wasn't holding charge.

the battery was dated 2012, and the previous owner had let the car sit for a while while trying to sell it, so it seemed to add up.