Yes, it's a confusing situation. Lets go through this.
Tsipras wished to avoid defaulting on the loan repayments...
That's a reasonably okay statement.
by asking for a new loan
No, that is new. (though everyone knew it was going to happen.)
Tsiparas wished to avoid default by having creditor institutions forgive some debt ("debt relief") and restructure the remaining debt ("debt restructuring") over a longer time ("the stability window" (within which Greece could grow without the threat of default looming over the economy.))
He did not want the debt to be rolled over by the creditor institutions. That is the referendum argument he makes ("no to short-term measures", "no to endless austerity", etc.), certainky not that a "No" vote means exiting the eurozone. In the letter he backs down from these demands and asks for a short-term rollover.
Why?
presumably because he hopes the ECB (a seperate body independent of the Eurozone group) would supply the liquidity to Greek banks they very, very desperately require.
At the same time he applied for a loan from the European Stability Mechanism (another different independent body (but with the same countries involved)).
However,
he later went on TV and repudiated everything above presumably for political reasons
Why?
Likely as his party is bickering with itself over supporting a YES or NO vote and he needs to show strength else his referendum, already farcial, becomes even more stupid.
It's a confused time, Syriza a confused party.
On your other point. Yes Greece has run a primary surplus. On the other hand it's dets is 1.8 times gdp, 3 times govt budget. At even a 5% repayment rate they require a prmary surplus of 15% of the government budget, a level that they have not even remotely come close to meeting. The forecast increase in Greeces DB pension liabilities and decline in revenue caused by the aging of its population means that even this primary surplus evaporates quite soon.
Why then would you loan money to a country who in no way raise the money to repay? Is this the balance on which you will rest your countrymen's pensions? Their social security?