Although i want to believe those numbers they are impossible. 2500 hours = 104 days. You really believe he spent 1/3 of his year just in development? So every single day he gets 8 hours of sleep, 8 hours of fulltime job, 8 hours of dev for this game, repeat. Its just not possible...
Firstly, there are 8760 hours in a year - so 2500 is closer to 28-29%.
Secondly, the job that pays the bills is 32 hours per week (19% of the hours in a week).
Thirdly, who says he sleeps 8 hours per day? The average adult does not get 8 hours (Even at 8 hours, that's 33% of the hours in a week).
Doing the math: 29%+19%+33% = 81%
Meaning that after working the job that pays the bills, and working on the game, and sleeping, that leaves about 19% or about 32 hours per week for family time.
15 hours Monday-Friday (3 hours per day)
17 hours Saturday & Sunday (8.5 hours per day)
Also, remember, some of those 2500 hours are his computer rendering those 'reused assets,' as you called them. Which means he can step away and enjoy some moments with the family while the computer is chunking away. Or he can communicate with fans and critics on here or on his discord or on other platforms.
That's not also taking into account any personal days he may take off from the one job and using those hours for development.
So, yes, Virginia, it is not only possible -- it is probable.
It's no different than the working parents I know in the US whose employers pay shit wages, so they end up working two full-time jobs just to put a roof over their heads, food on the table, and clothes on their kids backs.