Every $1,000 of deductions saves a typical sole prop ~$300 in taxes (income + SE). Tracking them year-round is worth more than any tax-prep trick at year-end.
Yes for anything over $75. Best practice: photograph or scan every receipt. The IRS does not accept 'I am sure I bought it'.
Yes — either standard mileage or actual expenses. If the vehicle is over 6,000 lbs and >50% business, Section 179 lets you expense a large chunk in year one.