Sell.
Even with 3 more pops he won't look amazingly more attractive on the transfer list and the time it takes and risks you take to obtain these you might get lucky and get 2 pops on a starter.
IF he had respectable OD I'd skill up to strong and then he would stand out on the TL but he is 3 off that and currently only has 1 skill above respectable (albeit a nice one in passing)
You could also go for 3 cheap pops in DR/HD/JS and then go for the sale when his JS is strong. Overall i feel the time spent improving him isnt going to be for much monetary gain and now is the time he can still attract a premium on his transfer fee based on age and attraction to many lower division managers for his versatility/wage and longevity appeal.