Crthuky

I'm new to this latex forum and with the help of the online platform tried to create a flowchart for my work. The code is quoted below. It would be a great help if the following codes are rectified to match my needs. Thanks in advance.

1) I wish to have the flowchart to be at center.
2)The arrows connecting the text box of 6-8 and 8-9 should not get overlapped.
3)The arrow connector b/w the text box 16-2 should be visible and also with 'YES' notes.

documentclassarticle
usepackage[latin1]inputenc
usepackagetikz
usetikzlibraryshapes,arrows
begindocument
pagestyleempty 
% Define block styles
tikzstylestartstop = [rectangle, rounded corners, minimum width=3cm, minimum height=1cm,text centered, draw=black, fill=red!30]
tikzstyleio = [trapezium, trapezium left angle=70, trapezium right angle=110, minimum width=3cm, minimum height=1cm, text centered, draw=black, fill=blue!30]
tikzstyleprocess = [rectangle, minimum width=3cm, minimum height=1cm, text centered,text width=3cm, draw=black, fill=orange!30]
tikzstyledecision = [diamond, minimum width=1.5cm, minimum height=0.5cm, text centered,text width=1.5cm,draw=black, fill=green!30]
tikzstylearrow = [thick,->,>=stealth]
tikzstyleline = [thick,->,>=stealth]

begintikzpicture[node distance=2cm]
node (start) [startstop] Start;
node (pro1) [process, below of=start] 1;
node (pro2) [process, below of=pro1,yshift=-0.5cm] 2;
node (pro2a) [process, left of=pro2,xshift=-2.5cm] 3;
node (pro3) [process, below of=pro2,yshift=-0.5cm] 4;
node (pro3a) [process, left of=pro3,xshift=-2cm] 5;
node (pro3b) [process, right of=pro3,xshift=2cm] 6;
node (pro3c) [process, right of=pro3b,xshift=1.5cm] 7;
node (pro4) [process, below of=pro3,xshift=2cm] 8;
node (pro4a) [process, right of=pro4,xshift=2.5cm] 9;
node (pro5) [process, below of=pro4] 10;
node (pro6) [process, below of=pro5,yshift=-0.5cm] 11;
node (pro7) [process, below of=pro4a,yshift=-1.5cm] 12;
node (pro8) [process, below of=pro6,yshift=-0.5cm] 13;
node (pro8a) [process, below of=pro7,yshift=-1.5cm] 14;
node (pro9) [process, below of=pro8a,yshift=-0.5cm] 15;
node (dec1) [decision, below of=pro9,yshift=-1cm] 16;
node (stop)[startstop, below of=dec1,yshift=-1cm] stop;

draw [arrow] (start) -- (pro1);
draw [arrow] (pro1) -- (pro2);
draw [arrow] (pro1) -|(pro2a);
draw [arrow] (pro2a) -- (pro2);
draw [arrow] (pro2) -- (pro3);
draw [arrow] (pro3a) -- (pro3);
draw [arrow] (pro3) -- (pro3b);
draw [arrow] (pro3c) -- (pro3b);
draw [arrow] (pro3) |- (pro4);
draw [arrow] (pro3b)|- (pro4);
draw [arrow] (pro4)-- (pro4a);
draw [arrow] (pro4)-- (pro5);
draw [arrow] (pro5)-- (pro6);
draw [arrow] (pro4a)-- (pro7);
draw [arrow] (pro6)-- (pro8);
draw [arrow] (pro8)-- (pro8a);
draw [arrow] (pro7)-- (pro8a);
draw [arrow] (pro8a)-- (pro9);
draw [arrow] (pro9)-- (dec1);
draw [arrow] (dec1) -- node[anchor=east] NO(stop);
draw [arrow] (dec1) -- +(6,0)|-(pro2);
endtikzpicture
enddocument