Sounds a bit over friendly. Is he trying to suck up to the boss?
Keeps looking at you, staring almost as though he can't take his eyes off you - weird
Always stops to chat when in the office - normal, friendly
Checks that you are OK regularly - depends how often? Has your stress increased and they’re concerned?
Fist bumps you regularly - if you’re not a fist-bumping type of office, weird
Regularly and subtley invades personal space (in a non creepy way). - crossing boundaries
Light pretend punches on your upper arm - over friendly
He looks/ glances at you when in conversation with other
Always complimenting your work - friendly to over the top
Says things like 'I always have time for you' and 'I really look forward to the days you are in the office' - a bit creepy
Always has your back on work related stuff. - ok
Keeps saying you can go to him if you need to vent about anything - once or twice fine. More, overbearing