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For speaker transformer, do you mean the field coil, or the audio output transformer? The speaker itself should have 3 or four connections (it depends on if the field and voice coils share a ground connection). The field coil should have about 1330 ohms across it, according to the schematic, while the voice coil of the speaker should be something like 5-6 ohms (it has a hum-reducing coil in series with it).
These old speakers use the field coil as an electromagnet, as well as a filter in the power supply for the whole radio. Hence, if the speaker is disconnected, it will kill the power to the whole radio.
If a field coil speaker is dead, fret not, modern speakers can be used. Simply hooking up a modern 8 ohm speaker to the radio's old voice coil connections will get you started, and to make up for the missing field coil, put a fat 10w resistor of 1300 ohms value or so across those old field coil leads to replace it. This isn't to say that your speaker is necessarily bad; but I figured I would cover the wonderful world of electrodynamic speakers while we were on the subject.
....Although now looking at your readings, it looks like your rectifier tube may be working, and the next thing down the line that would kill your radio's B+ would be your speaker-isn't this fun?
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