Sounds like you need some tips for navigating the very unique soil and growing conditions in your area. I suggest you start with a local nursery and ask about the garden clubs or contacting the Master Gardeners in your area. Even neighbors with lovely landscapes are a good source of information on what grows well. As for your melons with black ends and thyme that died I suspect the soil you improved was so rich that it drained poorly and that caused root rot on thyme and fungal infections on the melons. When you improve the soil with compost and manures be sure to mix it with the existing soil and remember that clay soil drains very slowly so gardening in a raised bed or adding grit to the clay will help along with organic matter. Lilacs like cold winters so perhaps you can learn to love magnolias or some other bloomer that thrives in your area. Don't give up, gardening is an adventure and always teaches new things. Keep growing, Marianne Binetti