My husband and I both have individual living trust investment accounts.  In addition to ourselves being trustee of our own trusts, we are also both trustees of each other's trusts.  So although we each have our own individual social security numbers associated with our own individual living trust investment accounts, we can both transact freely on both of them as trustees.  

One trust had an investment which had a large capital gains distribution in 2018.  Filing a joint return will put us into a whole other tax bracket; however, if we can simply divide all our investment returns equally in half and file separately, it will put us both in lower brackets according to your "What If" scenario. Can we handle our investment returns in this manner?  (As an aside, I'm assuming my husband would have to report his W-2 earnings only on his own separate return, correct?)