1. Pershing graduated West Point 17 years(1886-1903) ahead of MacArthur and was 20 years older. MacArthur absolutely loathed Pershing, their paths first crossing when MacArthur, himself, was a plebe and Pershing was assigned tot he Military Academy.
2. The history you read about Roosevelt trying to get Pershing promoted a couple of years prior to Pershing's marriage to FE Warren's daughter is somewhat revisionist and only somewhat true. The timeline would cast aspersions on any and all debates about this subject. When Pershing's marriage to the Senator's daughter appeared inevitable, President Roosevelt tried to go through normal channels to get Pershing promoted to colonel. When Congress did not comply, Roosevelt bided his time, offered up some plum ticket punching assignments, then eventually capitulated to Senator Warren's cajoling and promoted Pershing to brigadier general. Pershing's promotion to brigadier general totally circumvented Congress.
3. Pershing was nowhere close to first in his class at West Point. General MacArthur was first in his respective class, but Pershing was not. Pershing was also 26 when he graduated West Point, and had only attained the permanent rank of captain in 20 years of service before getting the huge promotion(Yes, I understand things were different a century ago. In today's military, one would be asked to resign their commission if still a captain after 20 years)
4. As for substantial backup, one would have to check with the historians at FE Warren AFB to see if they are still telling the same story told at base orientations 30 years ago.