In case anyone is interested, here's what the Mavs situation looks like per my current spreadsheet.
One note: it appears I jumped the gun on Lawson being waived. I thought he had been; but perhaps not, at least not yet as KL asked below. If he hasn't been, his salary is not guaranteed (so he can be waived at any time before the season opener, at no cost) --- but until they do so, they can't add anyone else, because they don't even have minimum salary to sign anyone (only 1.58M). So I'm leaving this without Lawson for the time being, to make it easier to see what they might have left to work with on another player.
One note: it appears I jumped the gun on Lawson being waived. I thought he had been; but perhaps not, at least not yet as KL asked below. If he hasn't been, his salary is not guaranteed (so he can be waived at any time before the season opener, at no cost) --- but until they do so, they can't add anyone else, because they don't even have minimum salary to sign anyone (only 1.58M). So I'm leaving this without Lawson for the time being, to make it easier to see what they might have left to work with on another player.