A teacher should not be setting homework for parents to do. Many parents are unwilling or unable to help their child complete homework, and it is discriminatory for those children to be penalised as a consequence.
An IEP is an Individual Education Plan. They are for any child who is struggling and benefits from having individual targets. IMO, every child should have one, so they are definitely a positive thing, and should help your DS and his teacher to make good progress.
A SENCO is a Special Educational Needs Co-ordinator. They are usually qualified teachers and every school has one. I would speak to the class teacher in the first instance, and then approach the SENCO (perhaps with the class teacher).
The most important thing at this age is to keep learning fun, as to make learning a trial is to set a child up for a lifetime of associating learning with stress, making it aversive. He needs to be set tasks which enable him to be successful, so that he can enjoy learning and build up his confidence; these should be interspersed with more difficult tasks which challenge him.
If he is unable to complete any of the work he is set, it is the responsibility of the teacher to set appropriate work, not the responsibility of the child to do it, or the parent to do it for them. The class teacher may not be aware of how much he is struggling, so letting them know is the first step to take.
Good luck, and please don't worry- a happy child is the goal!