Will I be sinful for my past grumbling and cursing of religion? And will I be rewarded for my current patience, praise of Allah, and seeking His forgiveness?

What you were doing by reviling the religion is disbelief (kufr), but repentance erases what came before it, and the one who repents is like one who has committed no sin. Therefore, you will not be held accountable for what occurred from you in the past, as long as you have repented from it. And Allah is capable of transforming your evil deeds into good deeds. And the more you patiently endure and are content with Allah's decree and praise Him, the greater your reward will be.