Hi,
You really are doing a great job. Re the nipple shield, nipple shields are often a good tool that can be used in the short term to assist your baby to latch. Babies are designed to breastfeed, and if they can't that means that something is preventing them, not that they just don't want to. Often the nipple shield will hit a spot on their palate that stimulates them to suck. It is fine to use if it helps. Your story is a good illustration of why we are so reluctant to use bottles in the early weeks at least. Rather than the bottle being easier, I think it's more realistic to say that the two forms of feeding are different - like driving a manual car or an automatic car. You can do both, but it might just seem a bit easier at the start with an automatic.
A 200g weight gain is fabulous - well done for sticking with it and solving the problems that were thrown in your way