It's too soon to be dropping any milk feeds. At this point, solids should not be a replacement for any milk feeds as bm/formula is so important for brain and body development. It contains all the nutrition, fat and calories that that is required for optimal growth. Most babies don't start to drop a milk feed until closer to 10 mos or later. As for drinking from a beaker or sippy cup, you really have to be patient. It can take a while for your ds to get used to it. Have you tried a straw? Or try removing the valve from the sippy so it is more free-flowing?
There are basically two things you can do: keep buying different sippies until you found one that he likes or stick to just one kind and eventually he will get it. BTW both of mine really like drinking from a straw cup.
HTH