I bench 120kg+ without a spotter (at 95kg body weight). If I were to fail disastrously, I might have a broken rib, but without collars on the bar the chance of a severe failure that cause me to drop the fully loaded bar on my chest is pretty much 0. I've put it down on my chest and rolled it off more than once, and it only causes a light bruise that's gone in a few hours. I probably wouldn't do much more than 1.5 times body weight without a spotter, but I'm assuming you're not there yet, as I suspect you wouldn't be asking those questions if you were.

And use the dumbbells. You can bench with them. Do sumo deadlifts (legs flared much wider than usual, and lift the weight between your legs - you can start with one dumbbell, and increase to two). Learn to clean the dumbbells for overhead presses and front squats. Back squats are tricky with dumbbells, so there you'll have to resort to the Smith machine, thouhg it is considered somewhat evil amongst many lifters (it is easy to end up lifting with bad form and an unnatural movement, and very easy to fool yourself by leaning into the bar), but it is better than nothing.

Frankly, until you start getting to dumbbells that add up to more than your body weight on every main exercise, there's not much reason why the lack of a proper bar should impede you, and dumbbell exercises have much to be said for them for stability.