On question 2
I can put some input on question #2, being a former army guy the idea of flying a 200 single pilot just doesn't come up.
As far as why you aren't authorized to use fuel transfer in flight, there is no reason not to except for liability reasons. The people making the rules for that company (and this includes the army, they do the same thing) assume that the person flying the plane is too stupid to remember to turn off the fuel transfer switch, thus running the plane out of the fuel imbalance limit relatively quickly. The way the BE-200 fuel system is plumbed, when you are using fuel transfer, the engine you are feeding to will draw all it's fuel from the side you are transferring from, thus depleting that side at twice the rate. Your idea that using transfer would deplete your pressure doesn't apply because selecting fuel transfer automatically energized the standby boost pump on the side you are transferring from (logically since you can't rely on the engine driven boost pump if you are single engine). This provides a higher pressure coming from the other side of the aircraft and since the fuel transfer line follows an almost direct route into the opposite engine you have a higher pressure than the standard engine driven pump provides. This is the reason both engines feed from the side you are transferring from, not because any valve closed on the side you are transferring too.
In fact if you run the one side dry, the fuel would automatically begin to feed from the remaining side since then the fuel pressue from the formerly sucking engine will now be more than the pressure coming from the formerly feeding engine's side and then both engines would feed from the remaining tank. In this situation you would probably get a fuel pressure low light in the cockpit until you activate the standby fuel pump on the remaining side to ensure both engines recieve adequate fuel flow.
Now, since the rate of burn of both engines combined can easily reach 700-800 lbs per hour depending on your power settings and altitude, forgetting and leaving it on halfway through a four hour flight can be a rude surprise as you attempt to flare for touchdown and reach your control stops trying to keep your wingtip out of the dirt. That's why a large fuel imbalance at low speeds is a bad thing.
My guess is that some knucklehead actually bent a BE-200 doing this stunt some time back and since then the lawyer types insist that it can only be done in an emergency situation (ie single engine ops). Because in the end it is the lawyers writing the FOPMs and not the engineers, it becomes a operational way of doing things even if the reason isn't specified.
The strange thing is that in the BE-1900 it is done all the time to keep the plane balanced and there aren't any different annunciators or reminders to keep that situation from happening in it, but there is no restriction on the books about cross feeding. This is even though the max fuel balance on a 1900 is a paltry 200 pounds.