(Image credit: Getty Images) Oil briefly spiked back above $100 Monday after President Donald Trump rejected a peace proposal from Iran as "totally unacceptable" on Sunday, but all three main U.S. equity indexes held on for modest gains amid a solid earnings season and more signs of strength for the market's major trend. "I would say the ceasefire is on massive life support… when the doctor walks in and says, 'Sir, your loved one has approximately a 1% chance of living'," Trump said to White House reporters today about the state of play in the Middle East. The front-month West Texas Intermediate crude futures contract was up as much as 5.2% to $100.37 per barrel and settled with a gain of nearly 3% above $98. WTI is up 47% since the war between the U.S., Israel and Iran began on February 28. From just $107.88 $24.99 for Kiplinger Personal Finance Become a smarter, better informed investor.…