A first grader who has to count on their fingers for 7 + 5 is spending all their working memory on the addition and has none left for the word problem it sits inside. The only way through is repetition, spread over weeks, in small doses.
That is what the questions-per-page control is for. Twenty problems a night for three weeks beats one 60-problem marathon on a Sunday, and it is the difference between a child who knows the facts and a child who can work them out.
Two places. The first is subtraction across ten — 13 − 6 is a different kind of problem from 13 − 3, and a child who has only ever seen borrow-free subtraction hits it as a surprise. The gentle setting on the subtraction sheets is guaranteed borrow-free, so you can hold there deliberately and then step up, rather than mixing both in one page and not knowing which one caused the tears.
The second is reversals — b and d, 3 and E, and writing a whole number backwards. That is a handwriting problem, not a math problem, and it is worth ten minutes of letter-formation practice a few times a week rather than correction on a math sheet.
How much practice should a first grader do at home?
Ten to fifteen minutes, most days, beats an hour at the weekend. Short pages are the reason this site lets you choose eight questions instead of forty-eight.
Which sight word list do you use?
The Dolch lists, which are public domain — pre-primer and primer for Kindergarten and early first grade, then the first-grade list. They are the words that make up roughly half of everything a beginning reader meets.
Can I mix subjects on one printout?
Yes. A weekly practice pack puts math, spelling and handwriting in a single PDF with a cover page, which is usually more useful at this age than three separate sheets.