I can't see any cherry tomatoes and I don't think they have a place in that recipe anyway - weird.
All you need is some meat (or not), some root veg, some stock, some herbs. No soaking, no measurements, don't use too much stock. If you need more add it later. Chuck it all in and cook on a very low heat or in a slow cooker for 6-8 hours. Impossible to get wrong.
Put spuds in the stew or serve with mash or dumplings = done
Once you get up to about 15 or 16 miles in training you'll begin to see how it's possible. Even if you have to walk some of it you'll realise you can get round somehow and it will give your confidence a boost.
As Mllsy says, if you are at 13 miles now you are way ahead of most. You've also got time to add in a few weeks where you can drop the mileage down and let your body recover - most people won't have that luxury either.