I've seen some videos on youtube where someone recommend a tar like substance to fill those holes and prevent moisture getting in.

I live in dry Colorado so basement moisture isn't my area of expertise - but here are a few things to consider.

You can also see that the dark spots on the tiles are moisture (it's been raining hard here.)

So far, no problem with moisture or other (although scuffs do show more on the whitish Coventry Oak, also ordered online.

I have sought to and successfully penetrated entities on more times than I can count.

No way I would let anyone do this...if you penetrate the membrane below, it’s guaranteed to leak.

Also, I have a feeling that the out of town mailers have less penetration to the right person...

I have known landlords who had to regrout floors because the urine had penetrated it and could not be cured. 

not sure if i mentioned this one... a few months ago the tenant called and said there is some moisture/water dripping from the kitchen cabinet under the sink.i went there and saw the entire inside of the cabinet is wet. it's been dripping for some time. i asked her why she did not call me earlier and she said, "I never use this cabinet". when i looked around, half of the kitchen cabinets were empty.

Did you check her ceiling with a moisture meter?