I did not realize how different the LB series was from the LK. I was hoping to see a pump similar to the ones on the LK models. That one mounts upside down from the LK.
I can not tell from the loader valve picture which is which. Usually they are stamped somewhere by each port. P=power in, T=tank and C=power beyond. Most likely on the bottom of your valve.
You are correct to locate the power beyond and check flow rate there. That will be after the diverter valve. The diverter also is splitting what flow you have for the power steering leaving very little for the loader and 3pt. This will probably be less than 1GPM at this point.
I would check on what pumps are available. Unfortunately the parts lookup does not show your model so I can not help with that. You may just need to call Michigan Iron and talk to them about pump options.