Hi Chester,
1. It's perfectly legal for individual owners to run their engines past TBO as long as the engine continues to pass inspections and the A&P signs it off as being airworthy.
If buying a plane under these conditions, the buyer should assume the engine day's are numbered (regardless how well the engine is performing) and the price of the plane should reflect this.
2. SPOH = Since Prop Overhaul
3. TSMOH = Time Since Major Overhaul (same as SMOH)
Good luck with your medical.
Jim
