OK, Toobie, I think I've got it. The reason it took so long is that you're talking about paralleling speakers, but you don't have enough of them.
Let's talk about the left channel. You have one amplifier channel and one speaker system. What's to wire in parallel? Asked another way, what do you have 2 of to wire in parallel? If you had FOUR speaker systems, you could run a pair in parallel per channel.
FORGET about all this. You have VERY limited power and NO 16-Ohm output tap from the transformer. Just connect the speakers to the 8-Ohm taps and hope for the best. If the system isn't loud enough, buy LOTS-more efficient speakers or LOTS-more-powerful amps.
And ignore all the gobblygook about biwiring. Biwiring speakers has nothing to do with wiring systems in parallel the way you seem to want to. (Of course, biwired speaker systems do have the 2 sections driven in parallel from one pair of amp taps, but that has nothing to do with impedance.)
To answer your last 2 questions, no and no. If you want to biwire a speaker system with only one pair of input terminals, you'll have to rewire the crossover to separate the 2 sections so each can be driven separately. 'Biwiring' has to do with separation by frequency bands.