Smaller site:
250 pages
Trusted by Google (shows snippets, top 8 in competitive keywords in SERPS)
Relatively new
No traffic by Bing (which means no keywords when researching pages in Search Console)

Bigger site:
1050 pages
Lost trust from Google (no snippets, much lower than should be for competitive keywords)
Much older
#1 in Bing (extremely important for keywords research)

I don’t want to move content from Bigger to Smaller because I don’t want to loose #1 rating in Bing and thus access to keywords research.

I would like to move Google trust from Smaller site to Bigger. Have anyone done this?

1.) 20, 50, 100 links from Smaller to Bigger?
2.) 301 redirecting some of the pages?
3.) 302 redirecting just to be on the safe side and have an ability to remove these in case of failure?
4.) Any other ideas?