The Leomon forgiveness is possible, certainly was the hardest thing to find so far. Might need a new game to get it right.
Generally choose things that are beneficial for the Banjo Brigade. Recruit more members, save friends.
But the most important part is easily missed. You need to avoid triggering the 1st sight encounter with Lilithmon inside the Twilight Ruins until you have gotten the Leomon Memories.
Once you have resolved the Leomon Memory maze. Trigger the encounter and Try to talk it trough. Suggest exchanging something for PawnChessmon safety. If you have the Leomon Memory, its a new trade option.
But at the end, refuse to give it.
After that situation is resolved, try returning Leomon memories, but this time... With Deep Trust.