Received Schedule K-1 for deceased brother's IRA after filing with substitute form 4852 with what I thought was final income amount. Did not receive as much as I filed?

Amend the return to remove the 4852  and add the K-1....

If the IRS accepts your return then you should wait on any Federal refund to arrive first, then amend the return by preparing Form 1040X to add the additional W-2 information.  If you end up having to prepare an amended return, it cannot be efiled; it has to be printed, signed, and mailed. 

In the meantime, do NOT make any changes in your original return.   If you have to resubmit or amend later, it has to start off with the return as you originally filed it.

What the Schedule K-1 (Form 1041) implies is that your brother's estate received the distribution from your brother's IRA and you received distributable net income from your brother's estate, not a distribution directly from the IRA.