esmith813 wrote:

Using SEO SpyGlass- How many back links should I find to assess competition? Or do I always need to do unlimited scan to get them all?

It's pretty much up to you. However, we'd suggest you to strive for
maximum number of links because this will let you identify the most useful backlink resources for your site.
esmith813 wrote:

We have a new domain. Our old domain has lot of back links that we would like to redirect to leverage the links.

The best solution would be to edit the backlinks so they point to the new domain. This will transfer more link juice than a redirect from the old domain would allow.