As someone whose good enough to maybe start futzing around with hardmode or a challenge statue, (but not both, yet) here's some advice.
First, it seems like your running into the classic blunder of assuming you've gotta take the ghosts in one siphon. This generally means that if you don't have space to position them to your liking, somethings going to come up behind you and eat. Siphoning for like, a half second just to force theme to disappear a bit is a valid tactic, and downright necessary when certain ghosts spawn on corridors.
As a general rule, you shouldn't be putting your back to walls or doors. Space is the commodity in this game. Without ghosts in your way, (as per half second siphon) you should have enough room to maneuver for another lantern charge even if you stand in the middle of a corridor. Alternatively, ghosts don't eat when stunned, so walking through them is still a possibility if your confident enough in the space you have.
Judging the lantern size is just a matter of experience, mostly? I guess? I've found it pretty instinctive, honestly, and slightly larger then expected at times. Judging hitboxes is a learned skill, and not transferable between a game like blood, and a top down twinstick-ish, no actual sticks involved, game.
Getting stuck on furniture is just a bit weird, outside of blackouts and the dilapidated, and even then a charged lantern and some effort into memorizing the room... Are your graphics settings correct/monitor brightness good? You should still be able to see in most unlit rooms, if a bit worse then a lit one.
Invinc frames are there to let you position yourself. If you could attack through them I feel the game would get a bit easy. Struggling free in a corridor can let you walk past pretty much everyone, and can set you up to take the current wave in a single fell swoop. A lantern charge while invincible would just let someone win by playing most of the game invulnerable.
Overall, there's a chance, haven't played the right variety of games to have the prebuilt skills to internalize timings and spaces and hitboxes? Practice is really all I can suggest if that's the case.
Also, I'm pretty sure you're intended to play this game with two hands.