With a mono-flow system you must take out the unused monoflow tees to keep proper water flow through the system If you have a 1 in x 1/2 x 1 in mono flow tee and then you cap the 1/2 you basically just have reduced the reset of the system by the flow that a 1/2 pipe can deliver. This is why they should be removed. Now as far as the basement loop. The tees should be installed at a distance that is wider than the total footage of baseboard heat. There should also be no other tees for anyother radiator between the baseboard monoflow tees. This is because of path of least resistance. If the tees are too close to eachother than the path of least resistance will be straight thru the tees rather than diverting down to the heat. Here is the trick of the day. When you have the heating system down you install a full port ball valve between the two tees and you then can shut it off when purging the system forcing water down thru the loop.
Not knowing exactly how you set up your system and where your bleeder or air vent is I can't help you much more.