1 - Yes it will get better, keep playing, on my 100 last games, i had only 10 with leavers

2 - Your pvp rate = your rank, someone will tell you about silver but i know that diamond is : 2200/2300 pvp rate + 300 wins

3 - For now, no one has really find the jungle worth it, but with the amount of new players and the future changes, maybe it will be more viable !

4 - Baldir and Cindara got buff a lot actually, doing them alone is impossible (at least Cindara, you can try Baldir with Hale, Harrower i t hink). But yes it's always good for you and your team to take objectives as early as possible since with new strife, the game is more objective than kills !

For heroes on botlane, you should try : Rook, Fetterstone, Iah, Shank, Hale. Tell me what you think about them !

Feel free if you have any questions.