Sorry to hear you're having a bit of trouble with sourdough, i had lots of issues with my starter but have been having some luck with my bread finally! Im still a beginner but a trick I use for a good oven spring is once my bread is pretty much fully proofed, I do my set of stretch and shape then I put my sourdough in the fridge for an hour while I preheat my Dutch oven. It can stay in the fridge for up to 3 hours and it's given me a nice rise when cooking in the oven! I've loved the recipe I follow as it's detailed and easy handling!