'06 350Z M/T

Issue
1. Recurring coolant leak and air in the system (resulting in heating issues etc). Coolant refill and bleeding cures symptoms but I already had to do this twice over 5000 km.
2. Funny smell in the car after 5-10 minutes of driving - not sure if this is coolant related (vs oil or sth else), but likely.
3. So far, one, not sure if the only source of leak localized with coolant residue on top of the radiator below the cap as well as belts and underlay - I thought it could have been the radiator cap itself, but after replacing it, the issue remains. Conclusion - faulty hose connecting radiator with the overfill tank or the spring clamp keeping it in place

Questions
1. Can I safely take off the rubber hose myself to inspect it? It seems to be attached quite firmly to the radiator, and I don't want to force it..
2. Can I replace the spring clamp with a worm clamp. My concern is that the plastic mounting could be easy to break. Alternatively I can order an OEM hose/clamp but it will take a month to arrive.
3. Is it possible that the leak in front of the engine bay contributes to the smell in the cabin? I didn't smell anything directly out of the vents (heater core leak?)...

Any other experience/knowledge based comments more than welcome I will document how the situation evolves.

 

You can remove the hose, it will be fine. If that's your problem, replace the hose and clamp.

 

Funny smell inside the car may be coolant. It is a "sweet" smell and easy to recognise. Coolant can get inside the car through the heating and cooling system. Difficult to troubleshoot.

Heater hoses may be difficult to remove because of heat and deterioration. Stubborn hoses may have to be cut. Have a new spare on hand.

 

The funny smell is probably the coolant (as others have said) being heated by the rad or other engine parts. It will migrate inside. Not likely heater core related - the smell is really strong (and fishy like) when that happens, plus you usually get steam from the vents or coolant on the floor.
It might be the overflow hose, but not likely. Gently twisting the hose will break it loose from the rad cap neck. If that doesn't work, carefully use a small screwdriver to get between the hose and it's connector. Take a close look at the upper hose connection and the core to tank seam. See if you can borrow a pressure tester from someone for the easiest way to find the source.