Omg im actually so happy to help. BIG Reply Im sorry
First of all, dizziness happens when youre pushing too hard and youre not super used to it yet. For example there was a point where I went from serious condition with 60 miles a week to running none at all. When I came back I was doing a wamup was going 7 min pace for the mile warm up felt great, but after I stopped I felt awful. Not winded or tired just super dizzy, it just has to do with conditioning, youll get it soon. And contrary to what you think running on an empty stomach is actually recommended.
Typically when its race day and its a morning-ish race I dont eat any breakfast but make sure to have a big dinner the day before. So I recommend eating 1-2 hours before running because running on a full stomach causes cramps, same thing with water. Make sure to drink a lot of water but none close to your running time or during a run, unless youre taking small sips during a work out. I think what made your dizziness worse is the mask since oxygen is very important when running (obviously lol its needed for everything). But also heat is very bad to run in, a hot day can make your condition feel so much worse than it actually is, so I recommend running in the morning while the sun comes up or in the afternoon when it goes down.
To build stamina you just need consistency, it sounds boring but thats all you need. A strat i know is to run for times rather than distance but still track your distance. For example, tell yourself "ill run for 25 mins today" then set a timer and check your distance when the 25 mins are done. Do that consistently and youll start to see that over time youll be running more distance in that 25 minutes just because youre used to consistency and youre getting used to it all.
An easy way to know when to stop is to have a set distance or like i mentioned before a set time. What I did when i first started was run 3 miles every day, no matter how hard it was, no matter how much I stopped I would run those 3 miles every day. I used to get them done in 30 mins, which if you do simple math is 10 mins per mile which is just really bad. Days letter soon I was getting them in 28 mins, then 25, eventually i could get them in 24 and felt fine to keep going, so then I increased milage not pace.
Thats a big tip, work on your base rather than your speed, speed will come naturally. I dont know your current running fitness but lets say you stop sometimes on your run, with consistency youll start to notice how you dont need to stop anymore, or as long as before. It all takes time.
ALSO BIG POINT: ITS OK TO STOP, dont let stopping discourage you, over time it will stop but like evrerything else it takes time, stopping is perfectly ok, everyone does it and sometimes you just need it, no matter how conditioned you are.