lots of questions.
yes, increase weight when you feel like its not enough. only you know your limits, just be honest to yourself. 5-10% weight increase is the typical amount to adjust by.
You might wanna lower your reps a little. 15 is great for a warmup, but functionally kind of useless. 8-12 reps a set is a better range. You can dip down to 6reps and really up the weight for targeting strength gains.
biceps....what do you do to work the back? biceps get used in compound pullilng movements...lat pulldowns, pullups, chin ups, and rowing moves. Pullups in particular are a crucial component to a good routine.
any bicep isolation exercise should be after all your back exercises are done, and shouldn't be too involved. a couple sets of curls at the end of your routine should suffice. biceps are not big muscles, so you don't need to hit them as much, particularly since you SHOULD be doing mostly compound exercieses, with free weights, which hit the biceps as well.
I'm not a fan of leg press to begin with. I feel its less safe to leg press than to do free weight barbell squats. I did something to my knee on a leg press machine, not even that much weight at the time, and later found out from even more experienced people how bad some leg press machines can abnormally contort your form.
switching to squats actually helped my knee heal as good as its going to (barring surgery, which is too extreme for the level of discomfort I experience).
Obviously I'm making some assumptions, quite possible incorrect assumptions, about your routine...the usual mistakes beginners make...and just trying to steer you in the right direction.
