Z retract & 1st Layer

Well I have done the basic tweaks and I think other then improvements or needs for certain prints or multiple prints the stock SD2 works well. I have recently made some larger engineered parts (4.5" diameter PVC spacers about 2" tall) and they are very accurate.

I did the zwobble, z stop nut thing (I want to add a small spring washer though) along with calibrate the temp and extruder.
And I notice with no covers on the front of the case I get small delamination on the front of prints but not too bad.

Two things I have noticed:

1: All those other things aside I can still print well even if few of the above are off. BUT after making my large part and the 2nd one came out like crap. I realized the bed was off from pulling the first one off. SO I re leveled and got better but I half-arsed it so I had to repeat to full level. About a 10min process. and whoila another even print. So Comment: I can not believe how critical a level bed compared to the other steps.

I leveled my bed with thick paper on the outside 3 points near the level screws and back the z down to zero until the paper just fits with slight pressure under the head. I now the middle of bed is warped cause that will not allow paper without much effort. but doing that does the trick.

I am wondering aside from a dial indicator. Anyone have luck using a bubble site glass? the bulls eye one?

2: With the bed level I see 2 things that I still like to tweak: the first 1-3 layers are critical.
I know my print is good when I even layers of infill going down looks uniform. Really good prints have all white lines with no blobbing. Now even with that some areas of the bed appear thinner (still smooth) but thin like thin ice see the kapton more and others might have few small blobs of plastic in the infill.

None of this effects the print after layer 5 and everything evens out but I think there is some bed warpness for some of it. but I suspect that that with interior perimeters I might have slight dragging. across small circles might be grabbing this plastic. If I lower/raise the zstop or relevel the whole print bed is off and the prints are shot so I know it is dialed in as best as possible and just in certain spots it appears. 

Will the z retract in slic3r really impact this? I am running at 1.9mm retract at 60mm/s and 0 z lift?

See the image below. couple spots where you see the drag or blobs in top left corner and bottom right corner. I improved that by lowering the flow rate down .1 and you can see near the middle edges the thin ice layers. I suspect that is the bed is hiigher at the middle then the edges and squishes down too much.

So is the z drag an issue? any tips
Bed as level as is, i might need to sand the middle down.

after a few layers you can see that even white smoothness but the top right corner still has what looks like a dragging? or possible is it just cooling from enclosure.

and then a bigger print that came out great imho but still had the first layers with similar issues.