As Stubbs said, first and most important, read the Help manual. That is the official documentation and it explains pretty much everything you need to know about the controls (despite what some people claim to the contrary, it is very complete). No need for wiki or Google or Yahoo or anything else online, really, as far as all important information, including all the things you mentioned.
Radiation is poison to your health (as it should be) so it decreases the available max health. Note that raw food, including old processed food (pre-war goods) has radiation but cooked food does not, so do not eat raw food if you can help it.
There are seven types of crops, each with different weight to caps value ratios. Plant crops to grow more food but check weights for anything you carry (melons and gourds weigh 1 lb each while corn weighs 0.1 lbs so you can carry 10 corn for the cost of 1 melon, much more efficient... although you really don't want to carry raw crops, anyway).
You cannot spam stimpacks or other healing items (thank goodness). However, there are MANY different healing items and the effects stack with each other, so it is easy to have a decent regen going by eating/drinking several things (as well as using a stimpack if you like). Stimpacks also heal crippling damage unlike food, so you may want to keep that in mind. No need for Medic except for eventually building the Clinic trader in your settlements (assuming you build settlements at all) and even then only Rank 1 of Medic is needed.
Power Armor is so ugly and clumsy I never use it (same with heavy armor in Elder Scrolls... or any armor, actually). However, it simply uses a fusion core for power and they weigh nothing, so simply carry extra fusion cores (and they are far too common for this mechanic to mean much as far as limiting the player who wants to use PA in any way).
Repeat: read the Help manual in the game. It is the official documentation and tells you everything you need to know about mechanics.
One more thing: pay attention to the tooltips and pop-ups during early play as these also feature instructions about various mechanics.
Remember that this is a role playing game so it has content and mechanics designed for a wide variety of play styles. You can easily make yourself overpowered by not role playing and simply gaming the systems, but that isn't how the game is really meant to be played as far as an RPG is concerned. Imagine a character concept, embody that concept, and have your character in the game behave according to that concept. Something may be possible for your character to do, but if it doesn't fit the character concept, you shouldn't do it, not as far as role playing is concerned. A different character may very well do that action due to being a different concept.
This also applies to perks, SPECIAL, and general development of the character. Pick things that match the concept and play accordingly.