Need advice on flashing and root.

A few question , hope the expert here could kindly help to answer as i am new to andriod.

Model: X98 Air3G ( C6 J6 ) - Andriod only (kit kat 4.4.4 )

Currently using Telcast original rom
Currently using nova launcher and have remove or disable all chinese app
a) I find the touch screen not so sensitive although usable.
b) Sometime it jam

Questions
1)So if i flash to new custom rom ( Mirek190 V6 Roms) will it help to solve the above problem ?
2)Do i need to root first in order to flash new rom ?
3)If the flashing stop/jam half way or failed , can i still restore to factory default setting ?
By press power and Vol- button to recovery mode

Flashing new Rom . i intend to use back andriod (no dual boot) and use current partition
4) Will be using Flashing system and wipe data option . Is it a good option?
4a) There is a partition table (partition.tbl) in the new rom folder ,will it re partition my internal sd card when flashing the ?


Thanks in advance.

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