Likewise, I only has exactly 30 days. Talking away 4 days for travelling, I have only 26 days to make the distance. I think I can make it from SJPP, but it won't be a stroll in the park. I will see how the plan work out.
As I mentioned in my earlier post in this thread, it depends on how much time you have and your fitness level.
You have several options in your 26 day timeframe. First, as already mentioned, start closer to Santiago de Compostela. Second, as you mentioned, walk a lot of km every day. You are talking about an average of 30km every day with no days set aside for rest, recovery, or for that matter, few side trips and little sight seeing. That kind of daily average will also mean you are not likely to see the same faces for more than a couple days before walking ahead of those you have met and, perhaps, connected with. In my opinion, you are also upping the likelihood of injury.
Third, you could skip a stage somewhere which, you will find, is blasphemous for me to even write on this forum. I now shudder just thinking about how someone may respond to this god-awful utterance. Skipping a section will also put you out of that familiar community of walkers you have met. There is something significant that can be lost in doing this, and I would think twice about it (and not do it if you can avoid it).
At the end of the day, the idea of starting from someplace that is a more manageable distance from Santiago makes sense. Pamplona (720km to Santiago, 27k avg day) may work, but doesn't (easily) build in any rest/recovery days. Logrono would give you plenty of time, but I think you miss several very nice days walking from Pamplona and the comradery of many other people starting from, or near, there. Frankly, though, Logrono is your "safest" - and best? - bet and gives you a little wiggle room.
That brings the conversation back to fitness. If your fitness level is good - and you get a little lucky and avoid tendonitis, bad blisters, and other injuries, which is unlikely - starting from Pamplona would be great.
You have a lot to consider but I'll wager, whatever you decide, you will have a wonderful Camino.
There is a point at which you simply must put one foot in front of the other and walk, regardless of where you start. Buen Camino!