Looks good! I had quite a pressing mishap a few years ago when I was making my 2nd Dunlop (see here http://cheeseforum.org/forum/index.php/topic,6739.0.html
). Doesn't affect the flavour. I put mine back in the mould with the slanted side down and pressed lightly for a while to try and correct things, and that worked pretty well.
Anyway, I don't use a pH meter, but I think the normal procedure is to rennet after there's been a change in pH (0.1 or 0.2 drop?) rather than when the milk reaches a set value. So, if it started at 6.8, you might rennet at 6.7.
Adding more mother culture at the start will shift you further along the acidity curve, but it won't "speed things up". Think of it this way. Every 20 minutes your culture doubles (I believe that's a rule of thumb I've read somewhere - the exact rate will, of course, depend upon culture, temperature, and a host of other factors, but let's use this double in 20 as an example). Now, if I put in 1 ice cube of mother culture, then in 20 minutes I will have as much culture as if I put in 2 ice cubes, then at 40 minutes I'll have 4 ice cubes worth, and at 60 minutes I'll have 8. If I put in 2 ice cubes right a the start, then at 20 I'll have 4, and at 40 I'll have 8. I've saved 20 minutes (the first doubling period), but the amount of culture (which determines acidity) is growing at the same rate (it still requires 20 minutes to go from 4 to 8 cubes worth).
What happens, though, is you get into a section of the acidity curve where acidity changes very quickly much sooner if you put a lot of culture in right at the start. This makes it very tricky to reach your other targets given the time frame because you can get too far into the acidity curve too quickly, and by the time you get to a particular step, the acidity curve is working against your other goals. For example, if you bump up the culture so that your acidity goes from 6.8 to 6.5, rather than the change of 0.1, then rennet, then wait 45 minutes before cutting, you will now be much further along in the acidity process and things will be changing rapidly (your extra culture and the extra growth time for that starting bit to produce a 0.3 change rather than 0.1 mean you are now out of sync). So now, after cutting, you might need to stir until a particular pH target. It's possible you've reached that already, so now you either don't stir, which messes up your moisture content, or you stir and miss your pH target!
Now, after saying all that, do recall that I don't use a pH meter, so I don't really have experience with monitoring what happens. There will be other consquences as well, and I'm sure those with more experience will correct my errors.
And, I'm sure this cheese will turn out just fine too!