Can I ask a bit more about your breastfeeding history?
You're mentioning prescriptions and supplements: do you mind me asking what you are taking (domperidone?) and what led to you starting to take them i.e what gave you concerns about your supply?
It might be that it is taking a bit of time for those supplements to take effect - domperidone for example can take a full 2 weeks to really kick-in.
It's also worth using pumping after a feed to try and work on your supply (and if you do use formula in the evenings I'd be tempted to try and pump if you can even if it's only for a little time as you want to ensure your breasts continue to receive the milk-making signals. Mums with supply worries who then supplement may find things decreasing further)
I personally wouldn't put too much emphasis on a yield as everyone responds differently to a pump and if you are feeling at all anxious about supply your letdown may be a bit unreliable when you are pumping. Instead think about your baby to judge your supply - are you happy with weight gain? Is he getting around 6 wet nappies in 24 hours (poo means nothing at this age as a healthy bf baby can go several days between dirty nappies)? When he's feeding can you see distinctive swallowing or hear swallowing sounds? Does he end feeds himself usually or when feeds end does he seem 'content' and satisfied?
I would say that you shouldn't put too much pressure on yourself until he is completely recovered from his cold. For all you know he has a sore throat and is gaining comfort from feeding. Or is especially dehydrated because he is fighting off the virus.
In a couple more days when you feel he is recovered I would make as your first priority (and keep goals simple and small) not letting him fall asleep with boob in his mouth (so in other words moving back towards EASY). You might want to look at this FAQ:
https://babywhispererforums.com/index.php?topic=52857.0Then once you feel that's achieved or mostly achieved so he has relearnt the basic technique of falling asleep at night you may find he transitions better between sleep cycles himself and wakes less. Or if not focus on resettling using other methods. I would suggest you then give yourself a rule that at night you do not 'allow' yourself to feed if less than X hours have gone since the last feed. Now you have to decide what X hours is - but gradually increase the interval. If he wakes before then you can use any other tool in your arsenal (including dh as suggested) but avoid the 'easy' option of feeding. It might seem easy now but in truth if boob becomes a prop it's not easy in the long-term. Don't say 'all night wakings will end tonight' - it's not uncommon for a 6 month old to have a night feed (see the FAQ on the BF FAQ board about sleeping through) - but force yourself to not offer boob if he has woken after a relatively short time.
As for the day - work on the pumping - offer both sides to stimulate supply if you aren't at the moment and also consider 'switch nursing' (going back and forth more than once in a feed to simulate supply). Keep a careful log if you aren't already - include day and night feeding and sleeping patterns and see what you notice.
