What is the ruling on combining Quranic verses and Prophetic Hadiths in supplication as a reminder of Allah's grace and good expectation of Him?

What you are doing is correct. Supplicating with certainty is religiously مطلوب (required), as is high aspiration in it. As for commencing supplication with Surat Al-Fatiha, there is no harm in it, as it contains praise of Allah, and offering praise is commendable in supplication. However, one should not always adhere to this, lest it lead you into an 'additional' bid'ah (innovation).