1. If Amex slashes your CL, it only affects your utilization. If you're not spending (much) on your Amex cards the effect is negligible.
Utilization is
30% of your FICO score. Whether or not you spending (much) on your AMEX cards in particular is only part of the equation. To illustrate, if across an entire revolving credit portfolio, one has $100,000 in credit lines, $50,000 of which is AMEX lines with zero utilization, with the other $50,000 being, say, Visa lines with 100% utilization, one's overall util % would be 50%.
If after an FR the lines are (for the purposes of the example) reduced to $1.00, the util % will go up to 99% thus causing a dramatic dip in the FICO score.
2. While inflating your income is a slight risk, it'll help you get approved and get a decent CL, which is definite. It might affect you adversely, which is a maybe (only if you get F/R'd).
It also happens to be illegal (if you're lying)