couple problems with the R/T

I have a couple problems with my R/T. my dad wants it out of his driveway so I need to take care of these things soon.
As most of you know, I just got done with building a 2.4l with srt internals…etc. I got it started and running fine with the stock ecu and 24lb injectors. I drove it 56miles with no problems, never went above 3500rpms. I put in 577cc injectors, hooked up megasquirt and changed the starter because it was bad. Once I finally got the MS running and idleing, the temp on megatune went from cold 70* and increased to 197* but once it got that high boiling coolant got shot into the overflow. So I shut it off and let it cool down. Next time, a couple days after it did the same thing. I noticed that the top rad hose was hot and had alot of pressure. Even with removing the themostat and changing the rad cap it still happened
Its not the fact that the coolant is hot, somewhere it is building alot of pressure. Any ideas what could be the problem? Pretty much everything is new. New themostat, rad cap, temp sensor, radiator, water pump, lower rad hose.
And the new problem is megasquirt related I had it idleing fine those couple times. Then the time after that I tried to start it and it was hard to keep it running during warm up and eventually stalled out. Now I cant get it started, its not reading rpms so its not getting fuel. I’m going to resolider the crank position sensor and maybe swap the sensor. other than that I don’t know what to do.
And the last problem for now is with the LC-1 wideband. The wideband is showing 5v in free air. But megatune doesnt read it. I’m pretty sure everything is set up properly too.

Is the MS setup to read that type of wideband? You have to tell it which wideband you are using. also, there is a wait period, where it takes about 30 seconds to a minute until megatune starts to read wideband signal, are you waiting that long?

What caused it to stall out when you were running MS? Often, that happens from way too much fuel, and thats why it wont re-start. Did you log it? And when did it stop getting rpm signal? Was it something that happened right then? i’d find out why you’re not getting rpm, and then I would log you starting to crank it. Hopefully that will help.