It has been a long time since I've played SH1. I believe amount you save only affects the star ranking. Endings are dependant on tasks you do in the game. You should be alright if you're saving a lot.
I don't believe Silent Hill 1 has endings based on number of saves or anything like that. It's about items found and actions taken. So I wouldn't worry about it. It's not a particularly long game if you end up with a bad ending on your first playthrough.
I know Silent Hill 2 has endings that are affected by like when you heal and maybe how you fight in the game.