Yes, you can fill the whole form in and not actually submit it that day. I filled mine in over a weekend but then waited to submit until the day after an ESA payment (that way I got a full 2 weeks run-on of ESA).
I wrote my request for a biographical phone call to my work coach. I also added that I have complex needs and was finding the whole process difficult but would do my best to comply with any requirements. I said I might need extra support at times with maintaining my claim and explained why. I actually got a reply very quickly saying they would take all this into consideration. They have actually all been very understanding and not at all scary.
I then wrote requesting alternative payment arrangements under the payments tab and this was set up when I had my phone call.
