Yah, that's looking really good. Pierce it, top to bottom and through the sides, in 2 weeks. Then, again 2 weeks after that (through the same holes if possible). The piercing let's the oxygen back into the centre, which will get the internal blue going again. The holes often plug up, hence the re-pierce later. You want the paste to develop at this stage, in a couple weeks you want the blue to kick in and do it's thing.
Make sure you take this out for 30 minutes each day to breath. Also, put the cheese on the cover of the ripening box, and then put the box on top like a lid. That way, when you prop it open a bit the opening is along the bottom of the container. Ammonia is heavier than air, so if the cheese produces some (and it will) it won't settle around your cheese but "fall away". If the cheese starts to produce an ammonia smell, air it out a bit more, and lower the humidity.
You're now entering the tricky phase of mouldy cheese production. You need to monitor how it's going and adjust things to correct any deviations. That, my friend, is where experience comes in, so just try things, write them down (and write down why you did it) and then later write down if it worked (being vague here on purpose as it's a general strategy). Anyway, ask lots of questions here if you're unsure as there are some very experienced blue cheese makers here who will have some good advice. Mine is, you are probably better to cut earlier, around 30 days, rather than try and take it out to 90 days. The form factor is short and wide, and stiltons are usually tall and thin, but also much heavier. Aging the full duration will overdo it for the smaller size. And, if you are a bit early, you can age it longer, but it's harder going the other way.