Read your thread with interest, now I am not in exact same situation as I am a bit more mature of age, however does not change the possible impact both training and work can have on a relationship.
I can only comment on the training part of relationship hardships, depending on how you plan to train, modular or integrated- it will regardless have a great impact on your personal life, private life, relationships, friends and family.
Many will NOT understand, specially friends, specially during the ATPL's and also probably during the IR training.
Myself I took full time study at London Met + Modular, I am married, and all was well thought out in advance. Still there was plenty of periods during the ATPL's that it really took a heavy toll on the relationship, and I saw several of my other class mates with similar problems.
One of our teachers told us in advance that during the 4 -5 month period, there was a very big break up percentage in relationships, during the 6 month ATPL course. I think it was good to be aware of this, as it was important to have often talks with your better half.
Distance learning is probably not going to be much easier, as you are probably stretching your exams periods with at least 6 months I would think. There was little time for friends or other family then the ones closest to me, many friends had very little understanding for this. The ATPL's are not difficult, but there is such a large volume of stuff you must get trough in relative short time.
After the ATPL's things got much better, during CPL and ME there was little problems, however again during the IR which I am completing now, there is possible more tensions to come, because again many people have very little understanding for the mindset required to get trough it, and still having your sanity left when you finished.
To my wife's defence, she has been amazing to understand me when I needed it most, even though I have probably been a pain, add to the fact I also had a baby now 22 months + full time business to run, maybe it explains some of the stress.
But yes, be aware already during start of training there will be some very hard times.
6 hours at school + travel + 2 to 4 hours revision time for just over 6 months, 6 days a week, that = ATPL's finish in 6 months.