The reason I asked about first & reverse with the vehicle stationary is those are the first place a clutch "drag" issue will reveal itself - clutch drag is when the clutch does not completely disengage and continues to provide some drive even with pedal fully depressed, and clutch drag is another reason you would have trouble changing down but not up.
On the particular model you have, the clutch is "self adjusting" and one of the quirks of the mechanism is that as the clutch wears, the pedal gets lower until it's engaging, literally with the pedal on the floor, and at that point clutch drag will occur because you can't push the pedal through the floor.
In your case, the pedal is at half travel, and first & reverse engage fine, clutch drag has been eliminated, leaving worn synchros as the most likely cause.