Ok first of good job nursing him back to health and for giving him a really nice setup that allows for pretty nice life quality, the only thing that could make it better is if the water was deeper, but with the modificacions already said it should be just fine. Very important tip: DONT feed him a woule big fish or big chunks of meat, put it all in bite size peaces and feed often small quantitys because softys unfornatly have the very bad habit of gorging themselfes in a quantity of food that they are no capable of processing, have unfornatly learn it the hard way That is also advizable for matamatas, no other turtle does that. Poor guy looks pretty beaten up, you should bring him inside for winter, spineys have a very large range and he may be from the souther parts where they dont hibernate. Probably lived like 23 years in a quitet river in the midle of nowhere, just to be cauth and treated like that