Since the vesting is done you own your shares and could work zero hours and still be entitled to them. The hard work you did over the 5 years as they vested means something.
But, if you want your co-founder to like his situation and work hard to make the company keep going I see this as like doing another round.
You need to raise X and valuation Y and dilute yourself accordingly. i.e. the company is in crisis because one of the co-founders is sort of leaving. To make up for that, raise some capital. Figure out the amount needed to raise and then work backwards from that number.
But, if you want your co-founder to like his situation and work hard to make the company keep going I see this as like doing another round.
You need to raise X and valuation Y and dilute yourself accordingly. i.e. the company is in crisis because one of the co-founders is sort of leaving. To make up for that, raise some capital. Figure out the amount needed to raise and then work backwards from that number.