Hi Louisabear
Welcome to the forum.
You might want to have a look at the following FAQ which explains where everything is;
www.benefitsandwork.co.uk/guides-for-claimants/faq/forum.
Thank you for your question, it is complicated but I will try and break it down.
1) You are quite correct when you say that your CB ESA will not be affected by the migration.
2) You do need to make a joint claim as your income will be taken into account for UC
3) Are you receiving CB ESA and in the support group? if you are, then you should not initially have to complete a new WCA form, you will at some stage after be sent a review form.
4) you will have to do a joint claim.
5) UC is digital by default but they do offer support to claimants who do not have access to computers, you need to contact the UC helpline: 0800 328 5644/5646/9344
You may want to seek help and advice from your local Welfare Rights Otganisation;
advicelocal.uk .
Gary