Ph and ppm at Harvest

Hello all
This is my first grow .
I have a couple of plants ready for harvest any time now
I have 3 questions
1 - the ph of my soil runoff is around 5 .I have been feeding with a ph of 6.8-6.9.
my question is,how high can i safely ph my water to compensate for the low ph in my soil?
2 - the ppm in my soil is very high as well .I am now flushing the plants.
What kind of ppm do i want to see at harvest time?
3 - from what i've read here ,you want to start flushing a week to 10 days before harvest.Depending on a lot of factors that could be anywhere from 3 to 6 feedings (flushes) .I guess that comes back to question 2. How many flushes before harvest or what ppm should i be looking for ?

Dolomite lime added to the top of soil will help to counter the acidic PH. do not add much, 1 teaspoon spread all around the top of the soil at first. PPM you want to use for flushing would be 0 PPM. plain PH corrected water is all it takes. Last 2 weeks should be flushing, so if you have to water every 3 days, well then 4 or 5 flushes.

Ty
I will try the dolomite lime on my next flush.but i was just wondering also about "ph"ing my water higher ,like 7.5 or somthing,to bring my soil runoff water ph up from 5 ?
I know about the ppm of the water when flushing and normally the ph.Just wondering if a soil runoff water at harvest should be 0 ppm
Thanx for your help

Urrr h20 has a ppm. I am after the same information. I am in sunshine #4. I look at my run off to notify me what is going on in the core. I guess I would bring my run off down as close as possible to the water used to feed/flush. Don't over water as this can suffocate the plant in soil like mediums. This is working but I do like to hear what number if anyone knows is the target as to 0 is impossible. My guess is there should be an ideal range. I hope my current method improves ur taste. Good luck.