The phrase "upon you" means that they are there to capture him. Alternate translation: "The Philistines are here to capture you" (See: [[rc://en/ta/man/translate/figs-idiom]])
Samson pulled out the fabric from the loom when he pulled his hair away from the loom. This can be stated clearly. Alternate translation: "pulled away his hair, taking with it the pin of the loom and the fabric in the loom" (See: [[rc://en/ta/man/translate/figs-explicit]])