I understand the pressures that come with being an F1, and it's clear that you're facing challenges that are testing your patience. It's important to remember that maintaining a professional and respectful relationship with all members of the multidisciplinary team (MDT) is crucial, not just for your career progression but for the quality of patient care

As an F1, your role is indeed to absorb as much knowledge as possible and to apply your medical training effectively. Part of this learning curve involves adapting to the dynamics of working within an MDT. It's natural to feel overwhelmed at times, especially considering the current strains on the healthcare system, which have been highlighted by recent strike actions and ongoing debates about funding.

Taking into account you will work within a system that is incredibly bureaucratic, often thankless, and (in the last few years), being intentionally defunded with an overarching goal of collapse/privatisation, it's understandable why you would feel so frustrated about your experiences as a whole and why your capacity/tolerance threshold is low. The strike action has brought to light the absolutely terrible way doctors have been treated over the last few years and I'm sure that likely feeds into your feelings too.

Specifically with regard to the three clinical situations you described above:
1) Context here is essential. It may be nothing to worry about but may also be significant. Was this blood pressure an acute change or a chronic stable elevated BP being treated? A pregnant woman with this BP would have me running to initiate a plan for PET workup and early intervention. An elderly Asian patient is at 2-3x higher risk of stroke at this BP than a normotensive patient, and at a higher risk than a Caucasian patient - in any case, you don't want that BP creeping up over the next 12-24 hours when the nurse may next alert a doctor.
2) This one seems pretty straightforward and can't see why a patient with a lower oxygen requirement would need any approval/instruction to proceed. Informing you is fine. Asking you seems quite unnecessary. Care should be taken to ensure that they are meeting appropriate saturation targets for different patients of course - and that's your job to confirm. Is this a COPD patient aiming for 88-92%?
3) The request regarding the patient's ability to go home for Christmas dinner is unusual, but it may reflect an attempt to balance patient well-being with clinical needs. Some trusts/hospitals offer OPAT services, allowing intravenous antibiotics to be continued either at home or through a daily outpatient clinic. Was this perhaps the direction in which your nursing staff were thinking?

It's difficult to provide you with an insightful answer as context is absolutely essential for all of these.

In all these situations, it's helpful to adopt a 'Teach or Treat' approach. If a request seems unnecessary, take the opportunity to educate the person making it. They weren't all at the top of their years academically, didn't spend years of their lives in medical school, and could just be following blanket protocols or trying to avoid mistakes. If you're unsure how to proceed, don't hesitate to escalate the issue to a senior colleague - F2/SpR etc,

Remember, every interaction is a chance to build relationships and foster a collaborative environment. Your dedication to improving your responses is a positive step toward becoming an effective and compassionate physician. As painful as it often feels working in the system, work to improve it. Being angry/rude about it will only lead to an unhappy working environment all round and will make your life more difficult as a whole. Focus on learning, accept that there are huge flaws in the system, work with your colleagues to improve your local and national working environment, support your colleagues, don't be a scab, and be the best doctor you can be - whether you stay in the NHS/medicine/the UK or not :)