I'm going to assume your not a troll and give a reasoned response.
On your first point regarding the abolition of welfare for those under 25 this is an electoral group that has a lower propensity to vote at all and most importantly has a lower propensity to vote Tory. In addition, most AB class voters will likely already cover their childrens expenses and find welfare cuts attractive, the only damage to the Tories here are from the C class voters (working class). Admittedly i don't support the policy myself and think that working class voters are key to winning but it's not quite the electoral suicide you describe overall.
Since the election both the Tory and Liberal votes have reduced but nowhere near collapsed and Labour has not gained that significantly. Polling averages only suggest a 5% lead for Labour but the gap does tend to tighten as we move towards an election.
I'm also not at all sure you have read the Ashcroft report here..
http://lordashcroftpolls.com/2014/01/project-blueprint-phase-4-the-proceeds-of-growth/Firstly it makes the point that 37% of Tory voters in 2010 (~13%) do not intend to vote Tory in 2015 right now but it does not make several key points which are..
1) 6% of voters who did not vote Tory in 2010 intend to do so in 2015 (4% of these from the Lib Dems, 1.5% from Labour). A further 3% are more likely to vote for another party would would consider voting Tory.
Interestingly this means that the Tory ceiling (if they retained all 2010 voters) would be as high as 45%.
2) Of the 37% about a third (~12%) don't know who they will vote for in 2015.
Statistically those who 'Don't know' are very likely to vote for the party they voted for at the previous election indeed this and the 'shy Tory' vote discovered were major contributors to the shock of 1992.
This means that the Tories will likely retain around 4% of the 13% that say they may note vote for them meaning a maximum loss of 9%.
2) More than half of that 37% say they want a Conservative government after the next election and 75% would prefer Cameron as Prime Minister to Miliband.
This means that's there's a fair chance that half of them will still vote Tory in 2015 anyway and another quarter probably lean to the Tories over Labour.
This means that of the 13% potential loss 6-9% are probably going to vote Tory in 2015 anyway meaning that only 4% are unlikely.
.....................
Overall we have a few scenarios...
Best case scenario - Highly Unlikely - 45%
Optimistic scenario - 38%
Probably scenario - 35%
Worst Case scenario - Highly Unlikely - 29%
...
Given boundaries its worth noting that the first puts them in opposition, the middle two put them in coalition possibly and the top gives them a stonking majority.
...
For the record my own prediction at the moment would be something like..
Lab: 36%
Con: 34%
Lib: 19%
Ukip: 9%
......
My own ICM swing analysis however suggests..
Lab: 33%
Con: 30%
Lib: 17%