When do you update the ad copy?

After 100 clicks, we compare the performances of two ads. We build a new ad to compete against the winning one for another 100 clicks.

Should I run LinkedIn ads?

It is likely that LinkedIn campaigns to warm leads (aka remarketing) could be a good fit, but LinkedIn campaigns to cold leads is only a good fit for a few narrow industries.

Why is the conversion rate higher when leads come from paid ads vs. organic?

The paid campaigns are always going to bring in higher quality website traffic than organic search results for a few different reasons.