Dodge B150 dies when driving and starting problemss

[Mathy10544]

[sorry for run on sentences and bad grammar etc]
i have 1989 dodge b150 that i bought 3 months ago and it worked fine and then one day i try to start it and just got a clicking noise and the next morning i tried to start it and it ran fine for a month then a month i drove around and parked car to talk on phone and it wouldnt start again and had clicking noise and i had to have it tolled home and the next morning it started fine and ran for 2 weeks then it wouldnt start and had clicking noise again so i asked ppl what to do and the batt voltage tested okay and i got a new starter from autozone and installed it and it still had the clicking noise after the new starter
so i asked autozone what to do and i tighten and clean the battery terminals and it started but it was stubborn to start but it started so i drove it around the block and 1 hour later i tried to start again and it wouldnt start so i tightened the battery terminals more and added petreleum jelly and it started and the next day wouldnt start again with the clicking noise... i am not sure tightening the battery cables was related to it starting because it seemed to be starting unpredictably anyway
so it wouldnt start anymore no matter what I did so i charged the battery and jump started it and tested it's voltage (said it was okay) and it still would not start and it had a new starter and everything
so i went to autozone with the old starter (the new one was installed in the vehicle) and the battery and they both tested fine and autozone charged the battery and said:
1. try to start with the charged battery
2. try to use a screwdriver and press it onto both terminals of the starter to start it that way
3. if it still doesn't start follow the clicking noise to locate it
so i did all 3 of those things and #2 just made sparks but it wouldn't start and #3 i followed the clicking noise to an item i took a picture of... later they looked at the picture and told me it was the starter relay so i bought a new one... before replacing the starter relay i brought the battery to be tested for a 2nd opinion and it tested fine and on the way out i accidently dropped it and it cracked so i had to buy a new one... i also bought new battery terminal connectors
before i installed the new starter relay i installed the new battery and the same exact clicking noise happened... no turn over etc
after i installed the starter relay the clicking noise disappeared but it was basically the same problem... it was just a faint grumbling noise and the engine would not turn over and van would not start
i was still using the battery terminal connectors from the old battery so now i removed the old negative one and unsheathed some wires and put it in a new one and after replacing the negative battery terminal connector the car turned over and the engine sounded like it was very close to starting but wouldn't start but at least now it was turning over
i replaced the positive terminal connector and the same thing happened
i tightened and made sure all connectors were very clean and nothing would start and i jump started the battery and volt tested it to be okay because i figured i was draining it from attempting to start so many times
i took a break and 2 days later i tried to start the van and it started instantly on the first try so i went to drive it to autozone immediately to have alternater and everything tested but on the way there (it is a very short trip) when i pushed on the gas pedal the engine did not rev up but i pushed on it again and it worked and i drove through a park with very steep hills just fine and after going through the park i pushed the gas and it wouldnt do anything and eventually the van stopped and i couldn't get it to start no matter what... the engine would turn over and sounded very close to starting but wouldn't start
i had to have the van tolled home and i took a break and 2 days later i turned the key and it started instantly but i am too afraid to drive it and i waited 5 minutes and turned the key again and it started instantly so i turned it off and now i am not sure what to do next
i am novice at auto repair so this is first project for me... i realize that 1989 b150 is old and, financially, i can get a better replacement vehicle but i want to fix this van for personal education purposes
review:
1. wouldn't start with clicking sound... car ran fine for 1.5 months after buying it without any problem
2. new starter, new battery, new battery connectors, new starter relay
3. now it starts but unpredictably... no more clicking sound and the engine turns over and i am afraid to drive it because it might die again
any help is appreciated