For question #1, you ask if 341 kN is too large a force for the cable.
Cable manufacturers have specifications on break strength. Look up what the break strength is for that cable and divide that number by 341 kN to get your Safety Factor.
For question #2, what do you mean lateral force? Which result are you asking about? You have gravity which is a lateral force. If you replace gravity with acceleration, so you can type in a higher or lower value than 9.8 m/s^2. What happens to the tension if you cut gravity in half or double it? Note that you have to point the acceleration vector in the opposite direction to where gravity was pointing. For example, if gravity was -Y then the same acceleration is +Y.
@jj77, I learned from you how to get cable models to converge using the INISTATE command, so thanks for that!