You are doing really well, breastfeeding a reflux baby AND having a toddler is a real challenge. You are doing lots for him. Each feed he has is SOOTHING his throat as breastmilk has antacid properties, you are looking out for him and doing your best to manage a very painful condition that has no easy solutions.
Before going for early weaning, how are you managing the reflux in other ways? I apologise if you have done these/are doing these already but it can't hurt to repeat!
Does DS spend most of his time in an upright/semi-reclined position? You can even feed like that if you want.
Have you tried feeding then tried giving a dummy?
That worked with my DD for a few weeks until she realised dummies didn't have milk in them! The sucking on the dummy seemed to help her not sicking up as her oesophagus was working to take the non-existant milk down rather than bringing it up. Also she wanted to feed as she was in pain and the feeding would make make her tummy even fuller making being sick more likely. Though she had minimal pain whilst feeding it was when she overfed she was in most pain.
Winding mid-feed (maybe even more than once)?
Baby wearing in a sling?
DD seemed to get less distressed in a sling so less likely to be sick. Another plus is you can do something with your DD while you are slinging DS.
If you do cut out dairy then expect to have to wait 2 or so weeks for a difference in DS. It takes a while for diary proteins to get out of your body. Has your Dr suggested you do this or is this because you feel DS is displaying some of the signs of dairy intolerance? See here for advice on diary
Give the Domperidone a little while to take effect. Is the dosage based on his weight not his age? Remember as he gains weight the dosage will have to be increased.
Is the chart being used the new breast fed baby chart or the old FFed baby chart. This could make a real difference to how his weight gain looks.
How much does he weigh now/at birth? Does he put on any weight between weighings (same scales I hope!) or is he losing actual weight week on week i.e. he may be going down the centiles but is he gaining anything?
Normal weigh gain is between 5oz and 7oz a week, though with reflux I always felt anytime DD didn't lose weight was a successful weeks.
Also see here for soem great advice on breastfed reflux babies.