Does that include all your if any costumes?
I would keep them stored in Tc and as suggested just don’t let the timer run out or your done for in that Tc.
Then I would use the recruits I get from maps and farming to level up costumes and then duplicates.
From my personal experience I found it takes about 1500 to 1800 recruits to Max a 5* depending on weather there are more 1 or 2 star feeders, so at your current Tc stored amount your set for the next new 5* when it comes up to be maxed so keep it up for a second one.
I myself although not at your current delema yet, always still keep 1 Tc at 11 which has about 10k worth of recruits in it with uncollected feeders and use it when I get a new 5* hero I haven’t already got. My other tc’s get used daily to feed my current heroes as I am currently also only 1 5* away from not have any new ones left thus will be attacking duplicates soon.
Your luck will change eventually and when it does you will appreciate the stored recruits, that a given,lol, I know I do.
I only just got the hotm (my fellow Frenchmen, lol) and had enough recruits stored in that Tc to have him levelled to 3rd tier instantly, took up all my food though for a couple of days but he got there super quick.
That’s one thing I appreciate about the offering in the PoV which allows us to keep our collected food/iron in our inventory till we need it… There should be a suggestion to be able to craft those to store our excess food/iron for future use.