Marrow Man
Drunk with Powder
It is important to recognize that singing something that is "based on" a Psalm is not the same as singing a Psalm. It would not be proper to consider those selections from the Trinity hymnal to be Psalms per se and thus satisfying the command of God to sing Psalms, as per the OP.
True. But hopefully it's a first step. We sing at least one psalm every worship service, but we often add a psalm-based hymn since regularly singing the psalms at all is new for many in our congregation.
Let me add that when I got here 5+ years ago, we sang ZERO psalms and had no psalter. It takes times to implement changes. The Lord has been good to us, and the new ARP Psalter (the one Benjamin recommends), which is mostly an abridged version of the RPCNA psalter, has been very helpful.