Ay, totally normal yan, mama! Ang guilt ng pagiiwan lalo na sa parents talaga, but honestly, you deserve your own space especially kung ikaw na ang sumusuporta sa lahat, your kuya's family, the bills, lahat. One of my mum friends had the exact same situation, at sabi niya, once nagbukod siya, nakita niya na mas okay pala ang relationship niya with her parents kasi di na sila nag-eexhaust sa daily stress, at mas na-manage din nila financially ang sarili nila.
For the talk with your parents, kailangan mo lang i-frame it as your family needing to grow and stand on your own, which is true, you have a 1-year-old and a partner na gusto rin bumukod na. Next year is good kasi may time kayong mag-prepare, at you can also explain na malapit lang kayo, hindi kayo lilisan completely. A few of us tried keeping the conversation gentle but firm, parents understand kahit masakit, lalo na kung alam nilang para sa future ng anak mo.
About the feeling of moving out, honestly, it's liberating pero may adjustment period talaga, especially kung homebodied ka. Even having your own space tapat lang (like the setup you're thinking) helps kasi may "us" time you and your family, pero makakalapit ka pa rin. Start with essentials lang first: bed, stove, dining table, pots and pans, you don't need everything right away, bili bili lang as you go, kaya mo yan!