1st Gen R53 Cooper S Major cooling system issues R53

I have been having issue with my cooling system for some time now. I'll start off and list the mods and mileage, it's an 02 r53 with 280k miles along with hps silicone hoses as well as some of the stock hoses behind the motor that route to the heater core inlet at the firewall and heat exchanger, I have a csf aluminum radiator and an eBay aluminum expansion tank, a new oem water pump as well. Been having issues with the expansion tank running dry and various clamps leaking at the lower of the expansion tank and radiator so I got them snug and replaced the expansion tank cap. Now for a while I've noticed occasionally coolant smoke coming from bonnet and not always been blow out from the expansion tank. Also seen a lot of coolant puddles under the radiator passenger side tank, then today discovered a leak at the core to the passenger side tank weld. Explains the puddle, it was hissing out with bubbles. The cooling system seems to have to much pressure but I can't figure out why it's got to be the expansion tank not allowing the cap to properly function. I properly bled the coolant when I did a all the work but still find it bone dry every day or two after constantly topping it off. I ordered the oem expansion tank to replace the aluminum one. I don't think I have a blown hg, the cylinders seemed to have low compressions at about 130 to 138 psi each but they held it. There is no coolant being burnt or at least no coolant smoke from my exhaust. Is there a cheap good choice for radiator replacement? I hate to buy a sketchy eBay one but shelled out 400 for csf and look where I'm at now. What should I do? I'm going to have to keep driving it because I work 20miles away and to my only car.

 

I saw this brand online too
http://www.autozone.com/autozone/parts/Spectra-Premium-Radiator/2002-Mini-Cooper/_/N-jkf3uZ9pdak?itemIdentifier=34143_827501_0_

 

Installed the spectra industries radiator. Fit perfectly and had no issues with it. Car seems to be running good now. No leaks yet coolant temps are good. The csf radiator began gushing coolant out of what looks like about a 2 mm crack now. Glad I got that off. Also got the oem expansion tank on there and changed my oil. Oil looked great had all 5 qts still after 2 months.

 

If coolant no longer leaks out I'll give my car 1 more shot with high temperatures. If it runs uncontrollably high 230+ keeps going up at idle in traffic then I'll verify there's no air in my system and if that's true then assume my head gasket is blown or heads warped. I did tell you guys that the cars coolant got to 260F for about 20 seconds once when a plastic T fitting snapped right? May explain my blown radiator and oscillating boost

 

I didn't have any fluid cross contamination. I have had to do the low speed bypass mod because the exposed resistor rusted through and stopped working. (Imagine that). I'll check the fuses and make sure it's not blown again.