Donna
If you don't think that the tick boxes allow you to explain your problems easily then you can cross them out and mark them "see below" or "see attached". You must still answer the question.
Be aware, ESA is not a walking test, it is a Mobility test! In addition to your walking, it considers your ability to self-propel a manual wheelchair over the same distances, you do not need to be using a wheelchair or even to own one for it to be considered. SO even if you can show your walking is restricted unless you can also show that you cannot self-propel the wheelchair you will still not score points.
Gordon
Nothing on this board constitutes legal advice - always consult a professional about specific problems