I am a substitite teacher in PISD and I have a 7th grade daughter.
Kids need parental support and I admire you for stepping up to help this child.
For a 4th grader, he should know a lot more than that. There are several websites you can check out that have printable worksheets, etc. www.abcteach.com is a good one. Also, check out the website for the school district you are in. They often have parent tools for helping children.
He should know multiplication tables way higher than 1-2. Multiplication is semi started in 2nd grade and by the end of 3rd grade they should master multiplying up to 12. Flash cards are a help. We give timed test for adding, subtracting, multiplying. It is a 2-5 minute test with 50 very simple problems. (Ex...5+4, 6-2, 5x5) Division starts in 2nd grade as well. Basic math facts are essential for him to be successful in school and when he gets out later.
Reading...certainly chapter books. Time him to see how many words he reads per minute. Fluency is important. Also, ask some comprehension question. It is fine for him to read alone but if he reads aloud to you, you can get a feel for how he is reading and he gets practice. We have reading groups and students take turns reading a page during this teacher table station.
It amazes me to see some of the work the elementary children are doing already. They cover a lot of ground to prep them for middle school and up. Elementary school sets the foundation for children to learn, practice and get good study habits.
One thing we have always done is reward grades with $$$. My daughter does not miss an honor roll and when she brings her report card home, she gives us the "bill" for what we owe her. It is an incentive that works well for us, not for everyone. Maybe he can work toward some item he really wants.
Since you only have 2 weeks with him, be a model and let him see you reading, etc. When you are at the grocery store (or any place you can find a way to teach), have him help with weighing fruits/vegetables, calculating costs of items you are purchasing.
Good luck.
Susan